Check out Knowledge Base Article 821430
XL2000: The Solver Add-in May Not Work When You Start
Solver by Using a Macro
Applies To
SYMPTOMS
When you use Excel 2000 and you use the Solver add-in,
you may experience the following symptoms:
When you run a Microsoft Visual Basic for Applications
(VBA) macro that starts the Solver add-in and that sets
the problem parameters, no calculations occur or problem
solving occurs.
-or-
When you try to solve a problem by setting the problem
parameters in the Solver add-in, you receive the
following error message:
Solver: An unexpected internal error occurred, or
available memory was exhausted.
Note To set the problem parameters in the Solver add-in,
on the Tools menu, click Solver.
CAUSE
This problem may occur after you install Microsoft Office
2000 Service Pack 3 (SP-3).
Note Microsoft has confirmed that this problem only
occurs when you use the English version of Excel 2000.