This can be anything. It is a general message in WIndows that the software has done something illegal.
As DataEase is a programming tool there is always the opportunity to do something illegal but as it is a product there will also be bugs that cause this.
If you know what you do when it happens i.e. it doesn't happen randomly then the best way of getting around it is to program around it.
This means attack the problem in a slightly different way. Most of these things are so-called "corner cases" i.e.they happen when you do something in "unfortunate" in a "unfortunate" place so simply by tweaking it a little you can normally work around it.
The quality of the code in both 6.x and 7.x was a big problem and even though a lot of this was improved in 7.2 we have found a lot more (and fixed) in 8.x and now 9.x.
So the quick fix would be to first check your version of 7.x and download the latest 7.x if you have an earlier version.
If that doesn't help, try to download the final 8.x and see if that helps.
You can get a 30 day trial version here.