Does Office 07 recognize a combination of period and semicolon in filename?

I have a customer who is saving Word and Excel files to her computer and is placing a semicolon and period in the file name. Here are a few examples of the problem. If you name a file “1234;abccd” the file will show as “1234;abcd.docx”. If you rename the file to say “123.4;abcd” the resulting file is unrelated to Word/Excel yet it can still be opened. If you reopen and resave the same file “123.4;abcd”, the resulting file name will be “123.4.docx;abcd”.

The current version of Office we are using is SP1. This is the first time that this problem has come up and was unable to find anything on Google.