User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:2.0) Gecko/20100101 Firefox/4.0 Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 I've find the same bug on two computer. Ubuntu 8.10 i386 and Ubuntu 10.04.2 i386. In the same case I've the profile directory located on a vfat partition. After update at TB 3.1.8 (or higher) I can't update or install add-on. I've try to create a new profile on vfat drive and it doesn't work, another profile on a EXT3/4 partition work fine. On vfat drive I can work with TB (download, send or delete email) but I can't use add-on. Reproducible: Always Steps to Reproduce: 1.connect a VFAT drive 2.create a new profile on vfat drive 3.install an add-on or theme Actual Results: I give the error -203 for the new installation, for the update, I ever find the message restart to activate it (sorry but I can't remember the right word) I've found the same problem on two laptop, but I'm sure that if I make other test in other system I can find the same problem. The profile is located in a vfat partition so I can access from XP, GNU/linux and other Visualized system locate in the computer. This error appear only with TB 3.1.8 or 3.1.9

Do you also have the same issue with Firefox ?

I don't use shared firefox profile so I don't know is this bug is also for firefox. I can test it but not before next week. I'we try to downgrade TB at 3.1.6 and the bug is already present, but I'm sure that when I had install Ubuntu 10.4.1 all work fine, but I don't remember the version of TB included in the ISO, but please note that after installation I immediately have make a dist-upgrade.

Just test also with Firefox: Mozilla/5.0 (X11; U; Linux i686; it; rv:1.9.2.16) Gecko/20110323 Ubuntu/10.04 (lucid) Firefox/3.6.16 Also in this case, if the profile is stored in a vfat partition is impossible install Add-On or theme.

My Bug 683328 looks related: On Win7 (64bit) with Thunderbird 6.0.1 only one extension can be installed into a profile residing on a Ext3 formatted drive.

This bug is filed in a bugzilla component related to pre-Firefox code which no longer exists. I believe it is no longer relevant and I am therefore closing it INCOMPLETE. If you believe that this bug is still valid and needs to be fixed, please reopen it and move it to the Toolkit:Startup and Profile System product/component.