Full disclosure: I only read the first 2 posts, there are a lot of replies and your problem is already solved so no reason to read them all.
I can say, though, that this is somewhat of an area of expertise for me because I am a residential energy efficiency professional here in Dallas.
That being said, here is what happens with those AC powered electric fans in Texas - your region may be different, we have extreme heat around here!
The reason that your fan broke is because almost all AC electric fan motors break after a few years (5 - 6 years average here in Texas). They do have a thermal snap switch to turns the fan on at 90 or 95 degrees, and shuts off when the temp gets below that, but here in Texas your attic is about 120 - 130 F for 3 or 4 months straight, so the fans never shut off. This is what causes the motors to break - they are just over worked.
Furthermore, the electricity that it takes to run the fan exceeds the energy that you save from cooling the attic - again, regional differences may occur, but this is at least true in the south - see this study done in Florida:
http://www.fsec.ucf.edu/en/publications/html/FSEC-GP-171-00/
You do get benefit of reducing strain on the HVAC system and ductwork if it is in the attic, so even though you are spending more on electricity, reducing the temperature in your attic is important because this will increase the longevity of your HVAC system (if it is in the attic).
So, the conclusion is that for energy savings, solar powered attic fans are superior. If you go buy a fan at Costco or Home Depot or where ever, the DC electric motor will have the same problem - it will be broken after 5 or 6 years (at least in the south).
My company sells Attic Breeze solar attic fans. I am not employed by this manufacturer, and I do not receive any payment / commission directly from them. Attic Breeze is manufactured in Texas (outside Houston I think?) and they make the best solar attic fan on the market. It pushes almost twice as much air by CFM than other fans (solar or AC electric), and it comes with a lifetime warranty. They are larger and quieter than most fans, and you do pay a premium for the quality that you receive - but you will never have to replace it again.
http://www.atticbreeze.net/
If you are looking for an attic fan for your homestead, then I recommend Attic Breeze, hands down no contest. For rental, flip, or other investment properties, you may have to consider the extra cost that you would pay to get it.