Hi Tom...
I just did the same test and had no problems whatsoever.
- Created a new drawing with NO MODEL, no template, no format. This is a completely empty drawing with no parameters
- Created one single drawing parameter called myparam set as a string with the characters "XXX" as the value.
- Created a brand new symbol, added a circle (just so it had some shape to it) and a note. For the note, I entered "\my_text\".
- Under attributes for the symbol, I specified a free point as the location.
- Under the Var Text tab, I replaced the preset value of my_text with the string "&myparam".
- Saved and exited the symbol creator.
- Placed the new symbol on my drawing... and it shows up as a circle with "XXX" in the middle of it.
Here's the symbol in the symbol editor...

Here's the symbol on the sheet...

Here's the entire set of Drawing Parameters...

This is Creo 2.0 M080 which, I think we all can agree, is a terrible build code to use... but this is what I used for this demo. 
Thanks!
-Brian