I'm exactly in the same situation.
In general, applying for a visitor visa (TRV) while waiting for PR is allowed, and there are known successful examples from the past.
I've applied for a TRV just a few days ago, from U.S., and right on the next work day the visa office has requested my passport - I hope it's a good sign
I guess they don't request a passport unless they've approved the visa.
Detailed info on this subject here:
http://www.cic.gc.ca/english/resources/manuals/bulletins/2009/ob131.asp
Hope it's not too offtopic for this thread.