Edit the template.ica or default.ica on the WI server and make the changes below.

Change these lines:

Hotkey1Char=F1
Hotkey1Shift=Shift
Hotkey2Char=F2
Hotkey2Shift=Shift

so that they look like this:

Hotkey1Char=none
Hotkey1Shift=none
Hotkey2Char=none
Hotkey2Shift=none

This will prevent the Citrix client from intercepting these key combinations so they they are properly passed to your application.