Working backup 3 breaks

[reven]

Hi. I'm a little clueless on this one. I had a .mac setup working just fine, and backups on my server for over two weeks. I just returned from a weekend out and now backup doesn't work. I haven't made any changes to config so I really don't know where to start fixing things. Has backup been updated recently? My "About" dialog says: "Backup 3 version 3.1 (v356)".

Backup's log gives me a "Transaction failed for unknown reason (100) Unable to complete backup at this time." On the server side, I get this on the error log:
[Tue Jul 18 14:24:43 2006] [error] [client 192.168.0.4] Premature end of script headers: clientConfiguration.plist

And this on the access log:
192.168.0.4 - *myuser* [18/Jul/2006:14:24:43 +0200] "PROPFIND /*myidskdirectory*/ HTTP/1.1" 207 559 "-" "WebDAVFS/1.4.1 (01418000) Darwin/8.7.1 (i386)"
192.168.0.4 - - [18/Jul/2006:14:24:43 +0200] "GET /configurations/internetservices/backup/2/clientConfiguration.plist HTTP/1.1" 500 538 "-" "CFNetwork/129.16"
192.168.0.4 - *myuser* [18/Jul/2006:14:24:43 +0200] "PROPFIND /*myidskdirectory*/ HTTP/1.1" 207 377 "-" "WebDAVFS/1.4.1 (01418000) Darwin/8.7.1 (i386)"

I haven't been able to trouble shoot that 500 error. What does this file have to return?

Thanks for your thoughts.