The most common problem is getting the macro to run for the first time.
If you are having this problem, its likely that the Solver function is not installed correctly.
Some typical symptoms of this problem include:
1) Nothing happens when you press Alt, t, v
2) You get this error when you press the 'Fit Curve' button: Compile error: Cannot find project library
3) You cannot find the Solver in the Tools pull-down menu
First try opening the Visual Basic editor (Alt+F11) or Tools, Macro, Visual Basic Editor.
Then in the editor, go to Tools, References. Here you should see a list of
check boxes of Available References. SOLVER should be checked off. There might be something
labeled SOLVER Missing or something like that. In that case, you'll need to uncheck that before
checking the SOLVER. If neither of those are there then try going back to the Excel spreadsheet and
go to Tools, Add-Ins. There you should select Solver Add-In. You may need to have the
Analysis Toolpak - VBA checked off too, but not sure. Basically, you want to make sure that the
Solver add-in is installed. There are probably better instructions for going about this on the web.
Anyway, try some of these and let me know if you can get it working. If not, I might be able to
diagnose the problem based on what you found. You may even need to find your MS Excel or
Office disks to actually install the Solver (the default settings sometimes don't include this
when installing MS Office).