New top-of-the-line MacBook Pro suddenly starts acting old About a week ago, I got a new MacBook Pro. I work a decent bit in video editing, among other things, so I had the processor upgraded to the highest available model. The box arrives, I open it, and my word the computer is incredible. Battery life often surpasses 8 hours when running a host of programs simultaneously, everything happens instantaneously, El Capitan is spectacular, the force touch trackpad is incredibly click-like. Basically, the computer is everything I ever expected.

I install a few programs, go about my business, and about a day ago the computer suddenly starts acting weird. I'd definitely call myself a power user, so I'm not sure if it's something most people would notice, but the computer noticeably gets slower, battery life decreases to 4 hours on a charge with few programs running, the computer gets hot, internet misbehaves, and strangely enough, I think Safari acts differently, too. Until I tried Safari on the new computer, I had always been a Chrome person, so I'm not sure, but if I remember correctly a few days ago I could type a URL into the Safari address bar, click enter, and have it load. Now, I type a URL in and hit enter, and the URL gets selected, and I need to hit enter a second time to search. It's subtle, but I think it's a change. Moreover, Mail stops working properly, and now everything I send gets stuck in the outbox, I have this strange window that doesn't seem to belong to any program on screen:

I have clicked the bar and the search button, and nothing seems to happen. The App Store isn't trying to install updates, as far as I can tell, and the window doesn't change the application name in the upper left corner of the screen when I click it. I try opening Safari and get this friendly window:

So I am now typing this question in Chrome. I've downloaded Sophos to see if it can detect any malware, but the scan grinds to a near-halt about 65,000 files from the end of the drive. The hard drive has about 50GB of files in it, and I certainly don't remember putting that much stuff in there in the past week.

Basically, the computer is acting strangely, and I have no idea why. Any ideas?
Have you tried using Activity Monitor to see what fishy processes are running? Also, you can try creating a new account and use it for a while to see if it's something that only happens on your main account. I'd recommend you to use something like iStat Menus to check on what's clogging your processing power, network, etc