IE 8, Flash 11 erase LSO cookies from Firefox

Running on  Windows XP. Since the latest Flash and Explorer combines clearing Temporary Files with Flash cookies, there is no way to prevent cookie deletion -- including those generated by other browsers. This is terrible for shared computers like this one. I do not have the option to create another admin identity. However, because a support person told another user to clear cache on IE (for security reasons), I lost all my Flash cookies (passwords, progress, etc.) on Firefox. No, I cannot get this other user to change browsers. Searching on the internet has found that even *with* administrative access, preventing deletion of Temporary Files is impossible.

I will point out that:

1. ordinary cookies are stored by each respective browser, and were not deleted

2. there is no differentiation in IE menus between temporary files in Temp/Internet Files and the LSO flash cookies

3. with my FF Better Privacy plug-in, I can turn off Firefox auto-erasure of LSOs... and still IE will delete them

Caches need to be cleared a lot, and as long as there's no way for me to separate my LSOs from LSOs generated by a different browser and a different user, even with a password into both browsers, every single time Temporary Files are cleared in IE, I will lose my Flash progress on all sites on Firefox. It's also a huge privacy challenge; what's the point of using separate browsers if I can check the LSO folder and see exactly where the other user has visited, and vice versa?

Any solution in Windows, or Firefox, or Explorer would be appreciated.