I installed the Win7 Enterprise RC 1 7100 build on my Dell T3400. I didn't install any additional drivers. After awhile my DVD drive would just disappear. You couldn't access it, it wouldn't be listed anywhere, it wasn't visible in Device Manager and scanning for new hardware didn't find it. The only way to get it back was to reboot the system. The DVD drive is the TSSTcorp DVD+-RW TS-H653F using firmware A02 with a release date of 4/29/2009 on Dell's driver download section.
I was able to resolve this issue by adjusting the Suspend Mode configuration in the BIOS. I changed the default factory setting of S3 to S1. Boot to BIOS, select Power Management, select Suspend Mode and change from S3 to S1. Save changes and reboot.