procmail / Netscape Mail

I have read past postings to this mailing list and the FAQ, but nothing
appeared to address this:

I am experiencing problems with procmail confusing Netscape's indexes. 
The symptoms are that messages marked as read will be marked as unread
and messages moved out of the inbox will reappear their.

I have implemented the use of file locking by adding a colon to my
recipe headers.  I frequently "Empty Trash Folder" to update indexes but
this does not fix the problem.

Any ideas?