Acrobat Crash - Memory could not be read

First of all sorry if this has been covered before, I searched for a few keywords from my error but couldn't really find anything of any help. I am using Acrobat Professional 7.0 in conjunction with a VB6 program, which calls Acrobats JSO object to execute the menu item "save" to save a currently open PDF (which was also opened via the JSO). The program runs continuiously 24/7, and has no problems apart from the wee-hours of the night. At anywhere between midnight and 2am Acrobat crashes on executing the 'save' function with the following error:

"The Instruction at "0x2d864aa2" referenced memory at "0x00000008". The memory could not be "read". Click OK to terminate the program"

Any help much appreciated

P4 3.2GHz
2G Ram
XP SP2
VB6 SP5