I submitted a support case regarding this issue and the solution was to use a command line restore like this:
zmrestore -a
user@yourdomain.com -ca -c -lb full-20070602.010007.983 -pre restored6_ -restoreToTime '20070606.010008.454'
This will restore the user's mailbox using full backup of date 2nd of June 2007 and rolling out incrementals till 6th of june 2007. The restore will be done to a account called restored6_<user>. if you wish to override the user account being restored you should skip the -pre parameter.
This worked for me but note that the dates are exactly the dates of the full backup and incremental backup as they were taken in my system. Also make sure the backups include the user mailbox you are trying to restore.