File not found error

Hi
A few of times over the last month we've had jobs fail when trying to use the inifilesetkey JAL value with the following error

An error occurred while executing automation script: Line 54: Line 109: Error changing INI file. Not enough permissions or invalid file name.

The last time was early this morning

The ini file it's complaining about
a) Does exist
b) was certainly not being read by someone or something else; it's single-purpose and is only accessed once a day early in the morning
c) the domain service account that the scheduler runs under is a local administrator and has ntfs access to that file.

Also it's not predictable; I can't directly reproduce as it works with a rerun.

Is there anything you can think of that could cause this?

Any backup or antivirus software scanning the disk and locking the file?
Is there anything interesting in Windows Event logs and reported about the same time?

Also if this is a known problem, can you change the job to use OnErrorGoTo handlers to implement try...retry logic, in other words, to make the JAL script read the Ini file and the first read fails, wait for a couple of seconds and retry again?