When rebalancing a file, gluster creates a copy with the name ".$filename.gfs$filesize", e.g. ".foo.gfs3" for a 3 byte file named "foo". If the length of the file name is very close to the filesystem's limit (255 bytes in the case of ext3), then this operation will fail:

[snippet from the rebalance log]
> [2011-12-07 07:53:32.607413] W [fuse-bridge.c:184:fuse_entry_cbk] 0-glusterfs-fuse: 323262192: LOOKUP() /path/to/.somereallyreallyreallystupidlylongfilename.gfs40200 => -1 (File name too long)
> [2011-12-07 07:53:58.321882] E [client3_1-fops.c:2228:client3_1_lookup_cbk] 1-volname-client-1: remote operation failed: File name too long