I also receive the same error. Relevant information:
1) I created my account when Weave 0.2.0 was released.
2) I have successfully upgraded to, and used all the successive releases since then, including 0.2.4, the version currently installed.
3) I was able to login yesterday (2008-07-15), and that was with the same login information I am currently using. That was with version 0.2.4.
4) I reentered the saved login information in case it was somehow changed, this did not fix the problem.
My error log shows the same errors that others in this thread are receiving, specifically:
2008-07-16 09:08:35 Chrome.Window INFO Logging in...
2008-07-16 09:08:35 Chrome.Window INFO User string: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
2008-07-16 09:08:35 Chrome.Window INFO Weave version: 0.2.4
2008-07-16 09:08:35 Chrome.Window INFO Logging in...
2008-07-16 09:08:35 Chrome.Window INFO User string: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
2008-07-16 09:08:35 Chrome.Window INFO Weave version: 0.2.4
2008-07-16 09:08:35 Chrome.Window INFO Logging in...
2008-07-16 09:08:35 Chrome.Window INFO User string: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
2008-07-16 09:08:35 Chrome.Window INFO Weave version: 0.2.4
2008-07-16 09:08:36 Service.Main INFO Making sure server is initialized...
2008-07-16 09:08:36 Service.DAV WARN _makeRequest: got status 404
2008-07-16 09:08:36 Service.Main INFO Server has no version file. Wiping server data.
2008-07-16 09:08:36 Service.DAV WARN _makeRequest: got status 405
2008-07-16 09:08:36 Service.Util ERROR propfind failed Error code: 405
2008-07-16 09:08:36 Async.Generator ERROR Exception: checkStatus failed
From the looks of it, it's server side, so I want bother you anymore - I'm sure you're working on it.
Lastly, I'd like to thank the Weave developers, and the Mozilla developers in general for all their hard work. I know how hard it is, and how many of the most vocal early adopters contribute nothing other than loud, angry whining - despite the fact that the code is in the middle of development. Additionally, I think Weave has tremendous potential. Soon people are going to be shocked when their personal information isn't synced between the various computers they use - it'll seem archaic and annoying as hell.
So thank you for your hard work.