I have a file created with Excel 2010 that gives me errors when opened with Excel 2007.

I have several Pivot Tables, all using the same cache.
As soon as I try to expand an item, I get the error message.
If I refresh the table, I can expand once. If I try to do something else, I get the message again...

It works perfect with Excel 2010, and it does the same thing on other computers with Excel 2007...

Any advice?