Client crashing

We’ve got a customer site where the Navision 4.0 SP1 client keeps crashing on multiple machines. It’s been happening for about a month and we haven’t been able to determine the exact cause, but it usually happens when the user is accessing the Sales Header or Customer tables. I’ve gotten limited help from MS support and their most recent answer was to have me update fin.exe to build 4.01.22363. I implemented that yesterday and today the problem is back. Has anyone else been experiencing client crashes in 4.0 SP1? If so, how did you resolve it? All help will be appreciated. Thanks.