When your job entails doing IT support, you occasionally come across some odd behaviors. While it's pretty common in line of business applications or niche software, it's not every day that you find a fatal conflict between Microsoft Office and an HP LaserJet printer.
At one of my previous jobs there were two help desk staffers: myself as the Network Support Tech, and another guy as the Computer Operator. Most days it was pretty quiet, so it was nice when we got what sounded like a simple report: Outlook is missing when trying to copy and paste from Excel. Knowing how end users often report issues, you might come to a few conclusions initially. Perhaps the user is closing Outlook instead of minimizing, or maybe they aren't even opening it beforehand? Maybe they aren't actually copying in the first place? Thankfully, this user was one of our more knowledgable users, so we were able to assume he knew better than to make simple mistakes like that unless he was just having an off day. The operator was still running his daily reporting and data entry tasks, so I went to take a look. I asked the user to demonstrate and he was actually doing everything right: He would start a new email in Outlook, switch to Excel, and then immediatly upon copying the data Outlook would cease to exist as a running application. It didn't present any dialog boxes, confirmations, or anything of the sort. It would simply disappear.
I began doing my usual troubleshooting: I can re-create the issue, there are no entries in the Windows Event Viewer, there are no message boxes that are hidden offscreen, the process isn't still running, there are no log files. There is no hint as to why this is happening, leaving us nothing to go on. I run checks for malware, all clean. I run System File Checker, it's clean too. I run a repair on Office, no change. Even spending some time searching the web for possibilities turned up nothing. After all of this, we decided we will reformat as this is the only case we have ever seen of this happening. I bet you can guess what happened here: even after a reformat and fresh reinstall, the issue resumes. Since it somehow managed to follow through a reboot, we leave it as is. The user just has to remember that it will happen, and just re-open Outlook after the copy. It's irritating, but otherwise not that big of a deal. A little while later, the operator is researching the issue again and stumbles across an odd suggestion: Change the default printer. We get back to the user and try it, and it works. Thankfully the accounting department has a bank of printers, so it's not a hassle to print to one of the others by default.
In the end, it seems that there is some odd conflict between an HP LaserJet 4200 as a default printer while using Microsoft Office 2007 on Windows 7. If the 4200 is the default printer, then whenever you copy data from Excel, Outlook inexplicably closes without any errors or confirmations. If you change the default printer, the problem goes way until you change back to the 4200.