Thank you for the tips. Solved it, though it was different issue :-)
Tunred out to be a timesync issue. See: http://www.chriscolotti.us/vmware/gotcha-ntp-can-affect-load-balanced-vcloud-vmrc/
This is actually already the end of my response, but to be complete I will include below what I've found when searching for the error. Also was affraid it was in the SSL certificates, but the logs below show no issue.
I double checked and the Public Addresses I used in vCloud administration -> public addresses page are:
VCD Public URL: https://vcloud-poc.xxxxxxxxx.lan/cloud
VCD Public console proxy address: vcloud-poc-console.xxxxxxxxx.lan (in the logs I can see this address is used and seems to work)
VCD public REST API base URL: https://vcloud-poc.xxxxxxxxxx.lan
I enabled both cells again and the connection failed as expected. In the vmware-vmrc log I found the following:
==================== FAILED CONNECTION ==========================
When I shutdown either one of the vCells, I get a succesful connection. See log:
============================== SUCCESS ============================
*********************** SUCCES ************************
2013-03-23T13:18:59.099+01:00| vmrc| I120: Enabling HTTPS tunnellingvmClientCore::RunEmbeddedVMRC: parent PID: 6464, instance ID: "vmrc-np-t-{650939BD-5C39-4E0A-BA30-976C4E3B3192}", modes: 4, messageMode: 2, features: 3
2013-03-23T13:18:59.101+01:00| vmrc| I120: vmClientCore::RunEmbeddedVMRC: eventName = "VMRC_EVENT_vmrc-np-t-{650939BD-5C39-4E0A-BA30-976C4E3B3192}", monikerName = "VMRC_MONIKER_vmrc-np-t-{650939BD-5C39-4E0A-BA30-976C4E3B3192}", monikerEvent = 524
2013-03-23T13:18:59.101+01:00| vmrc| W110: IMonikerImpl::vmClientCore::MonikerImpl<class vmClientCore::InvokeMgrDisp>::GetTimeOfLastChange invoked
2013-03-23T13:18:59.102+01:00| vmrc| I120: USBGW: Write arbitrator op:8 len:8
2013-03-23T13:18:59.270+01:00| vmrc| I120: Setting proxy environment variable: "VMWARE_HTTPSPROXY="
2013-03-23T13:18:59.270+01:00| vmrc| I120: cui::vmrc::VMCnx::Connect: Connect to MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan"
2013-03-23T13:18:59.270+01:00| vmrc| I120: Resolving IP address for hostname vcloud-poc-console.xxxxxxxxx.lan
2013-03-23T13:18:59.271+01:00| vmrc| I120: Resolved to 172.17.1.94
2013-03-23T13:18:59.301+01:00| vthread-5| I120: VTHREAD initialize thread 5 "vthread-5" host id 1696
2013-03-23T13:18:59.378+01:00| vmrc| W110: SSL_IsVerifyEnabled: failed to open the product registry key. Falling back to default behavior: verification on. LastError = 0
2013-03-23T13:18:59.389+01:00| vmrc| I120: CertificateCheck::CheckCertEmbedded: allowSSLErrors: true
2013-03-23T13:18:59.389+01:00| vmrc| I120: CertificateCheck::CheckCertEmbedded: Found the following errors for vcloud-poc-console.xxxxxxxxx.lan's SSL certificate: {
2013-03-23T13:18:59.389+01:00| vmrc| I120: - 134217859
2013-03-23T13:18:59.389+01:00| vmrc| I120: - The certificate is based on an untrusted root.
2013-03-23T13:18:59.389+01:00| vmrc| I120: - A certificate in the host's chain is based on an untrusted root.
2013-03-23T13:18:59.389+01:00| vmrc| I120: - The host name used for the connection does not match the subject name on the host certificate.
2013-03-23T13:18:59.389+01:00| vmrc| I120: - The host's certificate is self-signed.
2013-03-23T13:18:59.389+01:00| vmrc| I120: }
2013-03-23T13:18:59.389+01:00| vmrc| I120: cui::CertificateCheck::CheckCertEmbedded - thumbprint for "vcloud-poc-console.xxxxxxxxx.lan" OK
2013-03-23T13:19:00.851+01:00| vmrc| I120: cui::vmrc::VMCnx::OpenVM: Cnx connected for MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan"
2013-03-23T13:19:00.851+01:00| vmrc| I120: VMMgr::OpenVM (cnx=vcloud-poc-console.xxxxxxxxx.lan, moid=vm-985)
2013-03-23T13:19:01.590+01:00| vmrc| I120: cui::HostMgr::OpenHost - opening host with MOID "host-32"
2013-03-23T13:19:01.592+01:00| vmrc| I120: cui::HostMgr::OpenHost - opening host with MOID "host-32"
2013-03-23T13:19:01.592+01:00| vmrc| I120: cui::MsgMgrVIM::Manage: Suppressing VM questions
2013-03-23T13:19:01.594+01:00| vmrc| I120: VMStatus: Unknown guest os type: windows7Server64
2013-03-23T13:19:01.607+01:00| vmrc| I120: VMMgr: Finished opening VM at /vm/#_3F151E0_vm-985/ from vcloud-poc-console.xxxxxxxxx.lan:vm-985
2013-03-23T13:19:01.607+01:00| vmrc| I120: cui::vmrc::VMCnx::OnOpenVMDone: VM opened for MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan"
2013-03-23T13:19:01.607+01:00| vmrc| I120: cui::vmrc::VMCnxMgr::EmitConnectionStateSignal: Emitting "connected" signal (requested) for MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan" - reason 'Connection successful.'
2013-03-23T13:19:01.607+01:00| vmrc| I120: cui::vmrc::VMRC::OnActiveVMCnxChanged: Active VMCnx: MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan"
2013-03-23T13:19:01.618+01:00| vmrc| I120: SnapshotTree: Emitting refresh ([VMFS-042-R5-Tier1-CX3-40-01-PROD] APV001 (25a6245d-19ce-447c-84dd-9e49ff25c744)/APV001 (25a6245d-19ce-447c-84dd-9e49ff25c744).vmx)
2013-03-23T13:19:28.029+01:00| vmrc| I120: cui::vmrc::VMCnx::Disconnect: Disconnect from MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan" while "connected"
2013-03-23T13:19:28.029+01:00| vmrc| I120: cui::vmrc::VMCnx::DoDisconnect: Disconnecting from MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan"
2013-03-23T13:19:28.029+01:00| vmrc| I120: VMMgr::CloseVM: closing VM at /vm/#_3F151E0_vm-985/
2013-03-23T13:19:28.029+01:00| vmrc| I120: VMMgr::OnVMDestroyed: cleaning up after destroyed VM at /vm/#_3F151E0_vm-985/
2013-03-23T13:19:28.037+01:00| vmrc| I120: cui::vmrc::VMCnxMgr::EmitConnectionStateSignal: Emitting "disconnected" signal (requested) for MOID "vm-985" on "vcloud-poc-console.xxxxxxxxx.lan" - reason 'Disconnection successful.'
2013-03-23T13:19:28.037+01:00| vmrc| I120: cui::vmrc::VMRC::OnActiveVMCnxChanged: Active VMCnx: (none)
2013-03-23T13:19:28.087+01:00| vmrc| I120: Clean exit
