We don't know exactly where the fault lies, but we know now for sure what causes it, and it is easy to avoid. None of which become visible to the user. This situation leads to further instances of Reader being spawned (since it doesn't run.) when a user opens a PDF. This being that Citrix believes that it has closed the program, but in reality it still runs under the user on the TS. In certain combinations of client OS', Citrix versions and TS OS' combined with (all as far as we know) versions of Adobe Reader (but possibly other programs) you can experience this. We finally found the problem (more or less).

Some of the better posts describing the same error: The only solution suggested is to install the v 12 Xen (Citrix) client, but that doesn't help. Information on this is scarce, but we have been able to find a few posts on it. We have tried Adobe Reader 6, 7, 8, 9, X. We run Windows 2003 R2 fully patched as of now. This is at least partially because of patterns of use. It seems that only a few 5-10 of our 1000+ users get this error at all, and about 2-3 of them get it a lot more than the rest. We have been able to figure out that this happens consistently when the user uses the 'x' on the right click 'drop down' menu from the Windows taskbar in Vista/7 to close Reader, but it seems it can also occur when closed in other ways, although rarely. (We have tried enabling the service too.)

After a while an error saying referring to the DDE service may pop up, but this is bogus error message as far as we can tell.

The user/Citrix Control Panel can not see the process. When we look on the TS process list, we can see multiple acrord32.exe's, one for each attempt to open a PDF after the hang occurs.

Foxit reader keeps crashing windows 10