error 57121
 

I've made a few spreadsheets with Excel 2000 with some simple
UserForms and VBA in it. Later I opened one of these sheets on a
different computer with XP. Everything went well. I changed a few of
the data and saved the sheet and was very pleased with myself. But
when I tried to open the same sheet again I wasn't so pleased, because
I got the errormessage "57121" and I couldn't do anything anymore. I
tried the same with the other Excel 2000-sheets and every time the
same thing happend: I could open the sheet one time, but after saving
it couldn't be opened anymore. What to do?