I have also had problems with 5.5 and 5.5.1. When I tried to open the capture module, the computer did a cold boot. Going back to 5.4.2 fixed it. I went to 5.5 because it was supposed to recognize DV machines.
At first I couldn’t get 5.4.2 to work when I reinstalled it but realized that when I was installing it I was allowing the installation program to retain newer *.dll’s, etc. By asking they be replaced with older files, all was well.
I don’t see many complaints about this problem so I have assumed it is limited to the DL SP (and possibly other older cards) and that I’m one of the few left using such ancient technology.
Sometimes it’s easier to work around problems.