Hopefully this will be helpful to someone out there.
Recently my Citrix ICA Client [Receiver] no longer launched the remote desktop in Mint 13. After determining that the remote side did not have a problem [due to recent upgrades], I gave up on Mint 13 and tried my brand new LMDE 201403 install on another machine. Citrix successfully launched the remote desktop...until the next round of updates were applied to LMDE.
After looking at what had updated in both, I suspected Firefox 30 [FF30] to be the problem. So I completely reinstalled LMDE and applied changes one at a time with successful Citrix sessions between each update. The last updated was FF30 and then Citrix wold not launch the desktop. So FF30 was the problem.
I read the release notes for FF30 and saw that plugins were all defaulted to "ask to activate". I changed the Citrix plugin to "always active" and that solved the problem.
Don't know if future FF upgrades will default all plugins back to "ask to activate" but that will be a pain if it does. Easy fix but still a pain.
There is another post in Mint Forums in Spanish [I think] that appears to be dealing with this issue but I wasn't for sure so I decided to post here for other monolinguists like myself.