I'm using VFP7 Sp1

I have a form that has been working fine for 2 years. It has not been modified for over 6 months.
All of a sudden the 2 grids in the form are SOMETIMES having the RECORDSOURCE set to ''.

It ALWAYS does it under some conditions. But I can't figure out what those conditions are.

It NEVER does it when I log on (the programmer).
If it does it for for another user on a particular day, it does it the rest of the day (even after rebooting). ie: On Monday it may ALWAYS do it, but on Tuesday it NEVER does it.
It works the same on 3 different computers. 2 that are connected with a peer-to-peer network and 1 stand alone offsite.

The app is using individual PRGs (no exe file).
When I (the developer) log on a global variable is set (glDeveloper).
Here is the only differences I can find between the 2 different logons.

Main.prg
  lParameters tlDeveloper
  Release glDeveloper
  Public glDeveloper
  glDeveloper = tlDeveloper

  if glDeveloper
    set Resource On
    ***** uses \Windows\ApplicationData\.....\FoxUser
  else
    Set Resource Off
  endif
  
  local lcUserName
  lcUserName = sys(0)

  ..... more setup processing

  If !glDeveloper
    local lcResource
    lcResource = '\LocalFolder\' + lcUserName
    set resource to &lcResource
    do main2.mpr
    _Shell = 'Do ReadEvents'
  endif
  return

ReadEvents.prg
  ***** just a top level program so errors can "Return to Master"
  *****    and also can be toggled on/off without having to re-run Main.prg
  READ EVENTS
  return

I've copied the resource file that I use to the other users and the problem persists.
When I log on as a regular user (not developer) and clear events, the problem persists.
When I step through the program with debugger the problem does not appear.

Can anyone think of something I'm missing?

TIA