[Exim] Strange problem whilst using Reiserfs

Ok, I have a slightly strange situation, I'm running Exim 3.22 on a Suse 7.1
machine using reiserfs (the journalling filesystem). Very occasionally
people have encountered emails that have merged together - it looks like the
file isn't completely finished being written to before Exim starts appending
the next message. The reason is probably down to reiserfs, but I wanted to
ask if anyone else out there is running Exim with reiserfs and if they had
encountered similar problems and, if so, if they had found a fix ?
John