File locking

I'm running MHonArc 2.2.0 to archive some internal mailing lists.  I just set 
this up yesterday and it was working fine until this morning.  Now it archives 
2 out of the 3 lists and gives me this error on the other:

Trying to lock mail archive in ... path

I get a mail after this happens from the system telling me:

ERROR: Unable to create path/.mhonarc.lck after 10 tries

Any ideas???

Thanks,
Nathaniel Lockhart
Sybarus Technologies Inc.