A couple of readers have reported problems getting Explorer to save cache files to a RAM Disk or ShrinkWrap image - a technique used to minimize corruption problems that can occur if the cache files are saved to your disk. The symptom is that Explorer does not save the preference setting for the RAM Disk after a shut down. Reader Akua offers an explanation:
"Explorer 3.01 (as well as previous Explorer's I've run) saves the location of its cache folder by Volume-Reference. This is not recommended by Apple. This can cause the problem with saving cache files to ShrinkWrap etc.
A Volume-Reference is basically an index to the mounted volume. If you sometimes mount external drives, network volumes or any other volume (CD), it will cause the index of your temporary partition (which is mounted last) to change. Explorer will not notify you of this, it will simply start using the Explorer Cache folder in your Preferences folder. The only work-around I can think of is to check your cache location in the Advanced Preferences setting when you start up Explorer."