Excel Error message when copying/moving a worksheet

[lgerick]

Hi all...
I am having a problem that only just recently started happening.
When I try to move sheets in a workbook to another workbook I get the following error message:
A formula or sheet you want to move or copy contains the name 'A1', which already exists on the destination worksheet. Do you want to use this version of the name?
This repeats many, many times and I have to click yes until it ends . this only started happening recently. Any one know why and how I can fix this so it does not keep happening?

Thanks
lgerick