I just noticed that my AppData\Roaming\Adobe\Bridge CS5.1\Cache\ contains over 3 GB of stuff, mostly thumbnail jpegs of images. Is it safe to delete this cache?
It'd be better to buy a bigger disk drive.
If you go to Preferences and select Cache you have two options, one is to Compact the Cache, the other to Purge the Cache, either one of these options should help you.
Will slow down the running of Bridge as it will have to rebuild the previews, but you do have tools to manage