Environment: Citrix Presentation Server 4.5, Windows Server 2003, thin clients with dual monitors
Description: Found that multiple monitor configurations were not working as designed. Only monitor on the left side was showing up and nothing more.
Resolution: Utilized Citrix article referenced below to troubleshoot issue by modifying video memory configuration for ICA Session. Had to play with the setting a few times to get it to work right. Observed the monitor on the right show half a screen at one point, and a screen that did not line up properly, etc — until we got the right configuration in place. Clients with limited server memory may want to consider whether they want to allow many dual monitor configurations on, since it appears that it can use a large amount of server memory for video in these scenarios.