unreliable file deletion via script

[Kurt Kaufman]

I have a group of  950 small (25k) record stacks, each of which 
contains a separate business account. I have 2 shared stacks "PPR.rev" 
and "paymentReceipt.rev", as well as two "anchor" standalones.  The 
standalones serve only as navigational tools to open up PPR and 
paymentReceipt.  From PPR, it is possible to open any of the 950 record 
stacks.

Whenever any stack is opened, it creates (from a preopencard script) a 
Busy*.txt file, such as "BusypaymentReceipt.txt".  This is to prevent 
more than one person accessing a stack at a time.
All of the stacks have in their closestack script that which deletes 
the Busy file, for instance:

if there is a file "BusypaymentReceipt.txt" then delete file 
"BusypaymentReceipt.txt"

This almost always works perfectly, but sometimes, a closing stack for 
some reason fails to delete its Busy file.  I can manually delete the 
file if needed, but that's obviously not what I intended, and I 
certainly don't want to ask anyone else to do so!  Does anyone have any 
ideas why the busy file deletion is not entirely reliable?  Script 
problem?

I have this app in operation on WinXP Pro, and the stacks and 
standalones were built using Rev 2.02.  I do have Rev 2.5.1 on Mac OSX, 
so I suppose I could recreate the standalones and the two shared stacks 
on the Mac and move them over to the Windows network...that is, if 
there is a known issue affecting Rev 2.02 on Windows that might cause 
this problem.

TIA, Kurt