DOEVENTS() wouldn't cause this error directly but it would allow other events, like ON KEY LABEL or Timer, occur during your program execution. If you're using VFP version prior to 7, take a look at http://fox.wikis.com/wc.dll?Wiki~FastDoEvents~VFP for performance issue with do events. Don't you have an error handler in your program that logs all info about error?

>I have a doubt about the DOEVENTS command. I have a program, which uses a Do-Endo loop
>to scan through a table with over 2 million records. Within the loop, I am modifying
>a field in each record. The first release of the program was working fine. Then in the
>second release this error 'Invalid subscript reference' was reported. I do not have
>much information regarding the error and I am trying to figure out why that might
>have happened.
>
>One of the changes, I made in the 2nd release was to add a 'DOEVENTS' command in the
>'Do - Enddo' loop. I did this because, I assumed that this loop would take a long
>time and I did not want this program to slow down other windows events. Could this possibly
>be the reason for the error? Since I added DOEVENTS, will the program try to move ahead
>in code and run into this error?