Hi Chalkey,
I'm guessing you may have found something already, but in case you haven't yet, see below. I should disclaim that I work for the company that makes the product I'm mentioning.
We offer a commercial SDK called EasyPDF SDK that converts Microsoft Word documents (as well as a number of other formats) to PDF. Check out pdfonline.com for a trial copy if you're interested. It's a printer driver based tool that requires a Microsoft Word install and is thread safe and widely used on servers. ASP.NET is supported. You shouldn't have issues with hanging conversions as there are timeouts you can set and exceptions you can catch in case a given conversion stalls for some reason.
The API is pretty high level and looks something like this for a basic server side ASP.NET conversion:
Loader oLoader = new Loader();
Printer oPrinter = (Printer)oLoader.LoadObject("easyPDF.Printer.6");
WordPrintJob oPrintJob = oPrinter.WordPrintJob;
oPrintJob.PrintOut(input, output);
Cheers