The .ldb file would be in the same directory as your .mdb file.
Typically, it would only be there if someone is using the db but if the
db is out of sync to begin with, or you uploaded the compacted and
repaired version while someone was using the old version, the .ldb
would still be there.
I checked your site...
The actual error message obtained when friendly errors are turned off is
Microsoft JET Database Engine error '80004005'
Operation must use an updateable query.
/forum/forum_posts.asp, line 326
Basically, it's saying either the db or the directory it's in doesn't
have write/modify permissions. As it was working before in the same
directory, I'd bet that your ftp program changed the permissions for
the .mdb file.