Why do I see an absurdly large size for a particular file?

Issue

On our gfs cluster, we find a file with incoherent file size. When running "ls -l", we get:

-rw-rw-r-- 1 hrprod hrprod 72057594037927935 Sep 24 15:34 PSWTFIRX.C

Which is obviously impossible as the gfs volume is 250GB and du says the file is 2G:
# du -sh PSWTFIRX.C
2.0G    PSWTFIRX.C

This isn't a problem in itself except tar fails to archive the file as it thinks it's too large.

This may happen with other filesystems than gfs.