Forcing them closed through SQL will get rid of them, but won't stop it from happening again.
Just a few questions to clear things up and try to come up with a solution that will stop this from what seems to be a recurring problem.
The description of the problem says that the PC is freezing, so I was wondering if you're picking up these checks on the PC or on one of the workstations?
Are you getting a "check detail read failure" error before the screen blanks out?
Is there any pattern to the checks that are acting up? Started from the same workstation, same time of day, anything like that.
Without any real details, my first guess would be that they're being accessed from the same workstation. Very often, recurring check corruption like this is due to power issues at one, or all, of the workstation. This could be due to just flakey power at the outlet, or something with a motor, (like a blender), or a compressor, (like a fridge), plugged into the same circuit as the workstation. If there's a check being sent on a workstation when the power dips it can mess up the connection to the database and foul up the write process for the check details.