Hello,
I have seen a similar issue with another brand of EHR software that was recently upgraded. The upgrade now required a minumum color depth of 16-bit. The Citrix administrator must ensure that a minimum of 16bit is set both on the published application and the servers that are load balancing the same. On the client side you must make sure of the same 16 bit is set either on the Application set in Program neighborhood or the custom ica connection.
The error that you described hints to the fact that the Citrix farm you are connecting to have set limitations for the ICA connection settigns for display. This typically affects larger monitor or dual monitor setups. Basically, once a session goes over the specified amount of memory allotted for session graphics, they are forcing the client session to degrade color depth first.
The Citrix Administrators must work with you to determine what setting is best for your published application and hardware setup.
Try lowering your IMAC's resolution to a more standard settign like 1024x768 or 1280x1024 and of course make sure that the clolor depth is set to 16bit and it try again. Hope this helps!
