Strange Lisp response

[Chris.McNeilly@NL.CS.CMU.EDU]

I encountered a bug with either CMULisp or Unix yesterday.
I have a directory with over 1000 files in it and I wrote
a Lisp program that would create an accompanying file for
each file in the directory.  When I tried to create the
files in the same directory as the original files, I
received an error message when trying to open a new file
that the file already existed, when in fact it did not.
After establishing that I wasn't trying to open the same
file twice, I had Lisp :supersede the new file and it overwrote 
the original files.  Finally, I had the new files created in a
different directory and everything worked correctly.  The new
files had the correct name and the original files were still
intact.

Is there a limit on the number of files in a directory?  If so,
then Lisp interpreted "aab-ndx", for example, as "aab" and tried
to overwrite the original file "aab".

Very baffling.