Cloning error

Yesterday I started cloning an EBS environment. After running the preclone, I started copying the enviroment on our netapp filer.
After the environment was copied, I started the actual clone.
But when adcfgclone is trying to create my new controlfile, the following error is reported in my alert.log..

Fri Jan 4 10:30:01 2008
scumnt: failed to lock /oebs/pubtst22/pubtst22db/9.2.0/dbs/lkPUBTST22 exclusive
Fri Jan 4 10:30:01 2008
ORA-09968: scumnt: unable to lock file
Linux Error: 37: No locks available
Additional information: 300
Fri Jan 4 10:30:01 2008
ORA-1503 signalled during: CREATE CONTROLFILE REUSE SET DATABASE "PUBTST22"

It seems linux cannot lock the file that's needed to mount the database...
I searched Metalink and google, but could not find anything that could cause my problem.
Finanlly we decided to umount the complete mount point. But all directories were still visible ???
We umounted again, adn this time the directories were gone. It seemed the mount point was mounted twice ?
After mounting againg, I started the clone again. This time no lock problems.....

Fri Jan 4 11:04:30 2008
Successful mount of redo thread 1, with mount id 2212425917
Fri Jan 4 11:04:30 2008
Completed: CREATE CONTROLFILE REUSE SET DATABASE "PUBTST22"