"4" doesn't sound right... Disp value►Hex should always display four hexadecimal digits, not a single digit. Do you have MathPrint enabled perhaps? I know it can sometimes cause problems with printing text to the homescreen.

And that code is almost right. Just get rid of the ! before the If and it should work properly.

Here's an easier way. Make one program (SRC) and put the following code in it:
.RUN
:GetCalc("appv check",16)
:Archive "appv check"( the appv var token can be found by pressing 2nd 8 )
MAKE SURE to include the space between appv and check, that's what makes the appv hidden.
Compile it with Axe and run it. Then delete prgmSRC and prgmRUN.
This will make a hidden appvariable that will not show up in the memory menu.

Then in all your sources, put this code at the beginning:
:!If GetCalc("appv check")
:Return
:EndThis will make the program quit if the calculator doesn't have the hidden appvariable. So basically, only your calculator will work with the program.

Also while hidden appvars might be useful to prevent people from deleting them by mistake and losing save files and preventing cluttering the memory menu, it makes it much harder for people to delete them as they see fit (especially if archived, in which case someone could create a program with malicious intents such as filling the user's archive, forcing him to reset its entire content).