[Dovecot] Problem with flags

[Jeff Hoskinson]

Greetings!  I'm having a problem with flags not working correctly.  I'm 
using Mozilla Thunderbird as my mail client, and Dovecot 0.99.10.4 as 
part of Debian on a Sparc box.

The thing that doesn't seem to be working right is Thunderbird's Label 
feature, which uses custom IMAP flags.  I noticed that once I labeled a 
message, I couldn't un-label it.  I recorded this exchange between 
Thunderbird and Dovecot while using the Label/None command on a message:

5235 uid store 35 -Flags ($Label1 $Label2 $Label3 $Label4 $Label5)
* 35 FETCH (FLAGS (\Answered \Seen NonJunk $Label4 $Label5) UID 35)
5235 OK Store completed.

Even though Thunderbird is sending the -Flags command for all its custom 
flags, the message is still retaining two of those flags.

Just out of curiousity, I tried changing the flag of that same message 
to something different, and recorded this exchange:

5259 uid store 35 +Flags ($Label2)
* 35 FETCH (FLAGS (\Answered \Seen NonJunk $Label4 $Label2 $Label5) UID 35)
5259 OK Store completed.
5260 uid store 35 -Flags ($Label1 $Label3 $Label4 $Label5)
* 35 FETCH (FLAGS (\Answered \Seen NonJunk $Label4 $Label2 $Label5) UID 35)
5260 OK Store completed.

So it seems the +Flags command works, but not the -Flags?  Or does it 
have something to do with sending more than one flag at a time?

Any help would be appreciated.

Thanks,
-- Jeff