As you can read here and in other forums, the Premiere Pro CS 5.5.1 update causes problems with some Blackmagic configurations. In my case the timeline freezes on clips with effects dropped on - these clips are not shown or rendered anymore. Sometimes PPro quits and reported system error on one of the Blackmagic plugins. This all happend after the update to PPro CS5.5.1.
Here's my config:
Win7 Pro SP1
Nvidia Quadro 2000 (driver 275.89)
Blackmagic Intensity Pro (driver 8.6)
Now my solution:
After a day of try and error I've found out, that the file 'display.dll' in PPro's program directory causes the problems. I backed it up and then overwrote it by the file that comes with the 5.5.0 version. After that I haven't had any problems anymore. I cannot say why it works, but it works (for me).
So if anyone having trouble with Blackmagic and 5.5.1 update, give this a try. But don't forget to backup the 5.5.1 version of display.dll, because maybe this bug will be fixed with a future Blackmagic driver update...