Thank you for your post.
Windows 7 is relatively new, and only a couple of problems have been reported (http://filemaker.custhelp.com/cgi-bin/filemaker.cfg/php/enduser/std_adp.php?p_faqid=7454); none of them related to printing. However, it very well may be a FileMaker Pro problem, so I'd like to get as much information as possible.
What type of printer are you using? Is the printer driver Windows 7 compatible? Is this only occurring on machines with Windows 7? Do you have any other Windows 7 machines running FileMaker Pro 7 and printing successfully?
I know you said this is happening at random intervals, so narrowing down the cause is going to be frustrating for both of us. The next time this occurs, please have your client document what he/she was doing just prior to the crash. Also, document the other applications that were open at the time of the crash.
Please keep me updated with any progres..