(See the best response by Lummox JR.)
Descriptive Problem Summary: When joining a game from either the pager, the website, or a direct link, it will stay open for (at most) a few seconds before closing on its own. I have uninstalled and reinstalled BYOND multiple times, and have tried several different versions. My antivirus is not a problem, and my Firewall has every application associated with BYOND listed as an exception. Sometimes, I receive one of the following error messages, but never both at once:
Application has generated an exception that could not be handled.

Process id=0xef4245 (15680069), Thread id=0xefa1b5 (15704501)

Click OK to terminate the application.
Click CANCEL to debug the application.


Could not run dreamseeker.exe (error 00000005). Perhaps you should reinstall BYOND?

Numbered Steps to Reproduce Problem:
1. join game

Code Snippet (if applicable) to Reproduce Problem:

Expected Results: Game will launch

Actual Results: Game does not launch

Does the problem occur:
Every time? Or how often? Every time
In other games? Every game I've tried
In other user accounts? Yes
On other computers? Unsure, only own one computer.

When does the problem NOT occur? It always occurs. Sometimes no error message displays, even when the window closes.

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? No, but after the problem first occurred, all previous versions now have the same problem.

Workarounds: none so far
Best response
I've moved this to BYOND Help because this definitely isn't a bug. Something is wrong with your installation.

Clearly you're having a crash, so it would help to see the event viewer logs from some of these crashes.

I think you've also ruled out your antivirus way too quickly. This kind of thing absolutely smells of a false positive event in an antivirus program.
I should clarify that my only antivirus program is the default Windows Defender. I've done multiple tests with it turned on (and have scoured to see if it reacts to BYOND at all), and even more with Windows Defender shut down completely. Both yield identical results. Is there anything else I can do with Windows Defender that I might not have tried yet then?
I've now uninstalled, reinstalled, and tried launching games again, all with Windows Defender marked as disabled, multiple times. What other possibilities are there?
Could you show us what the error message is from the Windows Event Viewer? If you open up your start button's search bar and type in "Event Viewer" it should pop up. Inside of there, find the Application(s) section and see if you can find when DreamSeeker.exe faults, and show us that error. It may not be too useful depending upon what the error specifically is, but it's a start.
I may need help with that. I've been giving it a try for a few days now, and can't really find a point in the Applications section where BYOND (the pager or dreamseeker.exe) pops up in Event Viewer, so I must be doing something wrong. No errors pop up in the Event Viewer. I did already give the Errors that pop up in a separate window after each failure. Can't I get any advice off of that?