Firefox doesn't save settings anymore

Hi guys,

since I've updated my FirefoxPortable to version 3.5.2, all my settings won't be saved anymore. Means, the add-ons and bookmarks are still in Firefox, but e.g. settings for Tab Mix Plus are reset everytime I start Firefox. I tried reinstalling but it didn't help.
Strange thing is that the directory of FirefoxPortable on my USB stick is write-protected. I tried several times to change that, but directly after I do this, it's back to "write-protected".
I'm a bit nerved by this, so I'd be glad if anyone could help me on this

Thanks a lot in advance!

hergl