Here's one for the Weird & Wonderful thread...
A couple of weeks ago, I finally got around to reinstalling Windows 7 (final) from scratch on my laptop, replacing the RC that I'd been using for months. That all went well, but I was having some SERIOUS performance problems with MC. In particular, it was performing TERRIBLY whenever I was accessing media files on a network or external drive, especially if the Library files resided on that same network/external drive. CPU usage kept pegging out at 50%, and MC's UI would lock itself up constantly (it would "unstick" for a few seconds, and then lock up again).
Well, last night I figured it out and solved it, and I thought I'd share.
Turns out it was Microsoft Security Essentials, the new free Anti-Virus system from Microsoft (which is AWESOME, BTW). The odd thing is that this issue only manifested on my laptop. Even though I'm using Microsoft Security Essentials on literally ALL of my personal machines now, I ONLY experienced this issue on my laptop. No idea why that machine is "special" in this regard, but this tip might help others who are seeing the same issue. So, here's the story.
When I looked into it, I saw that at the times when MC was acting badly, it actually wasn't any of MC's processes that were sucking up all that CPU time... Instead it was a process I didn't immediately recognize called "MsMpEng.exe", which Google revealed to be part of the Microsoft Security Essentials (or the old OneCare) application. It is always resident on my systems, but normally doesn't consume any system resources at all to speak of.... Maybe a 1-2% here and there, quickly dropping back to 0%. However, nearly as soon as I opened MC, it would jump to 45-50% CPU usage (on a dual-core machine). If I was patient and waited, it would eventually drop down to the 20-30% range, and that's when MC would come back and would again be "usable, but very slow", which is how I'd been suffering through lately. I went into the Microsoft Security Essentials UI and disabled Real-Time Protection, just as a test. Almost immediately, the process dropped to a still-overactive, but much more reasonable 5-10% CPU usage.
So, that was it. Some sort of weird and only-on-my-laptop conflict with Microsoft Security Essentials. Luckily, the Microsoft Security Essentials UI isn't dumb, and provides quite nice "exceptions" capabilities. I simply went into its settings "tab" and then to Excluded Processes. Then, I added exceptions for:
C:\Program Files (x86)\J River\Media Center 14\JRService.exe
C:\Program Files (x86)\J River\Media Center 14\JRWorker.exe
C:\Program Files (x86)\J River\Media Center 14\Media Center 14.exe
And the problem was completely solved. MsMpEng.exe is now acting completely normally again and back to not using any system resources. Even better, MC is now working PERFECTLY.