If you'll recall early on I think you had a problem here because you had some code in the New() of a business object attempting to Fill. Do you by chance have any code in the New() of a business object that may be causing an error.
The reason the form goes away is because an error occurred. The problem with the DTE environment is that is doesn't like to expose error messages very much. It usually just snuffs them like you have seen. I am fairly confident the problem is with one of the BOs. Let me know if you see anything in the BOs. In fact you can temporarily exclude them one by one from the project until you determine which one is causing the error. To exclude a BO, right click on it and click Exclude from project. To add it back in just right click on the file and click Include in Project.
How do you know you have it narrowed down to a single BO? If this is the case, post the BO source code so we can look at it and see if there is something fishy.
And I wasn't really suggesting that you guys put error messages in for this. I was just venting about VS2005....I have so many issues with it, and coming back to my desk to find my IDE sending an error report didn't help. HAHA...