I have also been having routine crashes when working with sources. I had hoped your recommendation to install .Net Framework 2.0 patch would help. When I tried installing 2.0 I got the message that it was already installed on my computer. So I downloaded and installed the 3.0 and 3.5 patches which were on the same site. Then I opened FTM, went to Sources and tried to link a media file to a source -- CRASH!! No change. I guess I will have to keep waiting patiently (Hah!) for the FTM programmers to get their act together.
Thanks for the suggestion anyway.