Marcia,
The OLE error code you posted is the exact same as the one I encountered.
I managed to get the control properly registered, by running the setup wiz on the machine again and saying REMOVE ALL, and then re-installing! I don't know if this is a definitive solution.
One thing I noticed was that if I un-reg the control and run the foxpro app it would ask for the activex file to use through a FILE-OPEN dialog box. Once I selected the control (COMCTL32.OCX, in any path) it would self-register the control and work!
In searching for a solution I can across a FAQ from MS regarding activex controls and MSN. EVERY time you log on to MSN it tries to make sure you have the most up to date contols on your PC!!! It may decide to download updates automatically. This means the controls you install on a clients PC's can be overwritten! I presume the activex design allows for this constant updating, but somebody forgot to make MS aware of it. No sooner had I correctly registered the treeview for a client, than he goes home and logs on to MSN. Now the foxpro app is back complaining!
Also the latest MAPI control is incompatible with VFP5, and also I think the file open common dialog control! Makes you wonder!!!

Excuse me if I'm way off now, but your problem with the toolbar would seem more likely to be a problem in their datasource, assuming one is set.I've noticed bound controls diabling themselves when at EOF() or the like!
Otherwise nothing comes to mind.