>Well, this has turned out to be a very interesting saga indeed. The .h file error was so horribly out of place that I started thinking something really wasn't right. I run Zone Alarm Extreme Security and use Malwarebytes to scan on demand. Neither turned up anything but because I was truly out of ideas at that point and had already been unable to compile projects for 2 weeks, I took the computer into the nearby shop where I buy hardware. Their scans revealed that malware had infected Zone Alarm itself and wasn't being detected until ZA was shut down. Six days later (!) I have my computer back, apparently free of malware, and the compile problem is gone. I suppose others may have similar stories but this is one of the strangest things I've seen in the 25+ years I've been in this business.
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>I suppose the infection could have occurred during a brief period where ZA had to be shut down for installing something else. The combination of requiring security software to be disabled AND requiring an Internet connection during the install should be avoided. If I know in advance that the download is not the complete installation file, I will definitely order a CD! However, most companies don't tell you that up front.
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>Thanks to all who hung in there and offered great suggestions.

FYI - I would get rid of Zone Alarm - it's the laughing stock of all hackers.