
As to FinderPop creating that null process, that would be news to me.
Back in the day, the (null) process was OS 9 running in Classic mode! I take it you can definitely rule that out? FinderPop hasn't launched Classic to open your document, has it??
I don't think I do anything special, from what I remember I just ask the Finder to open whatever it is you selected. Or it's possible I might use Launch Services to open it, I can't remember right now but will have a look at the code and report back later (the code I'm talking about probably won't have changed in years.)
What happens if you control-command-click in that folder and from the resulting FinderPop "Contents" menu, select your .doc or .xls file? Do you still get a (null) process?