Intel pin: Instrumentate running process

I created a simple pin tool that dumps any win32 CreateFileW calls. It works fine, but when i try to attach it to an already running process, the process simply terminates. Tried with several applications (notepad, wordpad, internet explorer), same result. This is the command i use:

.\pin -pid 8804 -t dumpfile.dll

I got a tip to try and turn off multi-threading like this:

.\pin -mt 0 -pid 8804 -t dumpfile.dll

but it did not help. Also tried with another, out of the box pintool, didn't work either, so the problem is not in my pintool. Any ideas?

Thanks in advance!