using 2010 with 2007 file it changed formatting

[hawgrider1]

When i brought some work home on a sd card i worked in it with 2010 at home. At work the next day i opened the files up in 2007 and my columns that had numbers have changed to dates. If i did'nt use the files they remained correctly formatted. is this common?

 

[Andrew Poulsom]

I've seen it reported but I haven't seen a reason or solution.