Solver error
 

I've got the following error message while trying to run the Solver with a
VBA program:
"Solver: An unexpected internal error occurred, or available memory was
exhausted."

Interestingly, after I run the Solver function on the spreadsheet, if I
rerun the VBA program again, the error message is gone and the VBA works. But
next time, when I open the file, same thing occurrs again.