Vista + 2003 Office =?

Recently encountered a unique case. Our employee has Vista on the computer, and he uses the office in 2003 (he did not switch to the 2007th). Novell network So, if you open a .xls file on the computer from the network ( previously created in Win XP ), the file will crash and will not open anymore (it will increase by a factor of 15). It happens with every excel file. Checked on another computer (installed Vista and 2003 office) - the same thing.
Gee :)