Unable to lock

Receiving the following error trying to launch MHonArc on a NT server. Any
ideas what the problem is?

Thanks, as always.

E:\inetpub\californiaaviation.org\_private\mhonarc>mhonarc.pl -add
d:\mail\californiaaviation.org\users\airportuser\main.mbx -outdir
e:\inetpub\californiaaviation.org\_private\maillist\archive\airport
Trying to create lock ...

ERROR: Unable to lock
e:\inetpub\californiaaviation.org\_private\maillist\archive\airport after 10
tries