GOAL SEEK NOT putting Target value on worksheet

I have several users of Excel 2003 reporting that the GOAL SEEK function will not populate the target cell with the proposed solution. In otherwords, the first form pops up where the user can fill the 3 criterea cells (Set Cell, To Value, By changing cell) and click OK. They click OK and the next form appears (Goal Seek Status), which does display the correct Target Value (the Set Cell value), but when they Click OK again, it does not transfer to the worksheet target cell. I've witnessed this myself twice with different users. Restarting Excel does correct the issue, but I'm hoping to understand the cause. A couple of other points I should make: Calculations are set to Automatic and all other Excel options are set to their default values. I've searched many forums and have so far not seen a solution. I'm starting to think an addin Goal Seek replacement form may be the best choice. Thoughts?