The following transitions are currently GPU accelerated:
-Dip to black
-Dip to white
For an explination as to why some large stills will cause a red bar see here:
This is about the 2:45 white matte part.
Here is a quote from the help file about colored bars.
Here is the link: This is a CS4 but its the same in CS5
The red doesnt mean you wont get real-time playback but you might.
Your system looks like its just fine for real-time playback.
A red render bar appearing in the time ruler of a sequence indicates an unrendered section that probably must be rendered in order to play back in real time and at full frame rate. A yellow render bar indicates an unrendered section that probably does not need to be rendered in order to play back in real time and at full frame rate. Regardless of their preview quality, sections under either red or yellow render bars should be rendered before you export them to tape. A green render bar indicates a section that already has rendered preview files associated with it.
Thanks everyone for your help!