Saving from 2007 to 2003 - 2003 won't open the file
 

I have a user that has Excel 2007 - She saves the spreasheet in 2003 format
(Fiel is almsot 50 megs) When the 2003 user tries to oepn it, she get a error
message:
Excel cannot complete this task with avaliable resources. Choose less date
or close other applications
I have rebooted her machine and opened nothing but excel, same results
I have installed the 2007 compatibility pack, same results
THe computer is running WIndows XP Service Pack 3 with 2 gbs of ram
Any suggestions would be appreciated
Thank you