Credit due to Tom Pacyk (http://www.confusedamused.com) - From the MCM DL:
If you're going to use any SoundPoint phones that run pre-V5 Polycom firmware be aware of these limitations:
"We found our issue, but I just wanted to update everyone else in case they run into it.
Pre V5 versions of the polycom 3pip firmware (which also runs the spectra link phones) don’t like having the following characters in the Lync dialplan
D (capital d)
Any variables past $1
Since not all polycom 3pip phones can get to v5 it is something you could run into.
Hope this saves someone aggravation in the future. "