POE won't Start Anymore

The game won't start for me anymore. I play thru my Steam account. When I try to start the game, I get the usual box saying Steam is "Preparing to launch Path of Exile..." Then nothing happens.

If I go into Task Manager, it shows that the Steam Client Bootstrapper is running, but it doesn't show that POE.exe is running. All I can do is end the process for Steam.

I checked my log file (which is huge, by the way - 132 MB! Is it safe to delete this file occasionally?), and here are the first entries for the first time this happened:

> 2018/02/03 11:09:17 658725062 24d [INFO Client 6808] Enumerated device for adapter: NVIDIA GeForce GTX 550 Ti. Selected feature level: 45056. Max feature level: 45056
> 2018/02/03 11:09:17 658725078 13f [WARN Client 6808] Output for adapter NVIDIA GeForce GTX 550 Ti of \\.\DISPLAY1 has no display modes. Skipping.

It just repeats the WARN Client 6808 message from there on out.
So it sounds like it has to do with my video card. I tried updating my drivers 2 days ago, but the same thing happens. Any suggestions?

DxDiag didn't detect any problems either.

EDIT: Here's my DxDiag report:
https://pastebin.com/LbWcVqfC

AND to make matters worse, I discovered I'm also having trouble with my e-mail. I can send, but not receive. Which explains why I haven't heard back from GGG :(

So yesterday I spent about an hour scouring every old post with the words "game won't start" and I came up with a list of things to try. One of them was to go straight to the Steam directory and run PathOfExile_x64Steam.exe as Administrator. It didn't work. Path started, then nothing.

Just for laughs, I decided to try "PathOfExile.exe" as admin. It worked!

So now the question is, why would that work and not a normal start-up?