Fkwilliams
Firstly, Welcome to the Chandoo.org Forums
There shouldn't be any issues opening a 2007 file in 2010.
A few things you should try on the 2007 machine
1. Open the file using the Open and Repair file option
Goto File Open, select your file and then use the small down arrow next to Open to select Open and Repair
Once open, check the file and make sure it is all ok.
2. Save the file again and save a copy as an Excel Binary File (*.xlsb)
3. Try in 2010 again
4. In 2010, does the file need the same network, internet access or SQL DB access etc as the owner in 2007 has ?, make sure the person has appropriate access if required.
5. Try the Open and Repair in 2010 as well
Please let us know how you go!