The Premiere Pro CS5 (5.0.2) update fixes many problems, including many crashes, and it adds several features.
We have also been working with several providers of plug-ins, codecs, and hardware devices (such as Cineform and BlackMagic) to assist them in updating their software to fix some errors and crashes. Please take this opportunity to download and install updated codecs, plug-ins, and drivers from these providers, as relevant to your work.
When you have updated Premiere Pro CS5 and supporting software, let us know whether your problems are fixed.
See this page for details about the Premiere Pro CS5 (5.0.2) update:
Premiere Pro CS5 (5.0.2) update: bug fixes and CUDA support « Premiere Pro work area
Please report bugs that persist after the update here: