"If you can still reproduce this with current daily builds, then please file a new bug and attach /var/log/syslog and /var/log/partman to it. Sorry for the inconvenience."
I'll waive the "file a new bug" bit for now, but do that in future - it really is easier for us to keep track of, which results in better results for all of you!
... and indeed I said in comment 12:
"If you can still reproduce this with current daily builds, then please file a new bug and attach /var/log/syslog and /var/log/partman to it. Sorry for the inconvenience."
I'll waive the "file a new bug" bit for now, but do that in future - it really is easier for us to keep track of, which results in better results for all of you!