CSS Styles Not Displayed

As I mentioned in my previous post, titled "forums With Attitude" I am having a problem with CSS styles being displayed when the web page is served by Apache, but the pages display normally when they're simply opened from the desktop as html file under windows.
It's beginning to look like this is a malware problem. I just updated "Windows Defender", so I decided to go ahead and run the "quick scan". The scan uncovered a piece of browser malware (see image below).

Unfortunately, removing this did not solve my problem, so I started poking around with other things.
With "Firebug" a Firefox debugger ad-on, it showed that my stylesheet had been replaced with a stylesheet using made-up style rules that begin with the word "yuck". However, Windows defender either didn't find the cause of this, or the malware can defeat Windows Defender.
I suspect the latter because after Windows Defender supposedly removed the malware, I scanned parts of the system (windows) again using "Custom Scan" and I found that Windows Defender will not scan the "Users" or "Windows" folder.
So, no solution yet. Still working on it. But I just wanted to let you know that this problem may be caused by other means than those that the forum guru's stated.