Whenever I use the open/save dialog, the application freezes and I have to terminate it

I've researched this for a month before posting this. I have tried all solutions and I'm still having this problem.

Half the time when I do something with an application that brings up the Explorer dialog such as Open, Save, Save As etc. the application freezes and I have no choice but to terminate it. This happened most frequently with a video editor I used, sometimes after spending an hour editing the video all my progress is lost because I had to terminate the frozen app. This happens with Firefox, this happens with just about every app that summons the Open/Save Explorer dialog.

So far I have tried:

Using a different/default theme since I use a custom one. This appeared to solve the problem for the first few minutes as my video editor stopped freezing when clicking Open or Save video file. But then it froze on the 5th instance or so.

Deleting the ComDlg32 registry key. Sometimes this helps temporarily, sometimes it doesn't. Clearly useless.

Verifying my comdlg32.dll was not corrupt (sfc /scannow). It wasn't corrupt.

Unchecking "Launch folder windows in a separate process" in Folder Options in the Control Panel. This helped the most. Now the explorer dialog freezes only 10% of the time instead of 50%. But obviously the problem still persists so my question is WHY?

I've run into numerous problems as I upgraded to Windows 7 from XP. Not to say I never had issues on XP but at least basic things like this functioned. Basic usability is a frequent problem now since I upgraded with all kinds of random instances of design backwardsness as if I've downgraded.