Installing newer version of userscript over older one does not update entry in about:addons

[ferongr]

Currently about:addons tells me the userscript is version 2.21.1 while in reality (when editing the script and looking at the source) it's 2.21.4

STR

1. Install old version of userscript manually from https://github.com/MayhemYDG/4chan-x/zipball/2.21.0 . Note version in about:addons, Greasemonkey tab.
2. Go to http://mayhemydg.github.com/4chan-x/ and click install to install the latest version (2.21.4 at the time of writing).
3. Open about:addons again, go to Greasemonkey tab and observe version number. In my case it's stuck at the old one. Verify that the script is indeed updated (see @version at source)

Environment: Nightly 11.0a1 (2011-11-27), Greasemonkey 0.9.13

Edit

I restarted for today's Nightly update, and I noticed that now the version is displayed correctly. I also updated a different userscript (by manually installing the newer version from US.o) and the same problem manifests.

[arantius]

I did:

1. Install https://github.com/MayhemYDG/4chan-x/raw/2.21.0/4chan_x.user.js
2. User script tab of add-ons manager shows version 2.21.0
3. Restart Firefox (just to be safe)
4. Install https://github.com/MayhemYDG/4chan-x/raw/2.23.0/4chan_x.user.js
5. Open the add-ons manager -- it displays the wrong value
6. Restart Firefox -- add-ons manager displays the right value.

So confirmed, with Greasemonkey 0.9.13. And 2011-12-03 nightly.