First of all, the server gets a fairly low number of hits per day - about 8,000 daily entries in the log files for all 3 sites (that includes all images, pages, etc.).
The physical server isn't an issue. One of the 3 web sites gets about 7200 log entries per day, and that site, along with another, have no performance issues.
The ASUS server is running WIndows Server 2008 SP2 (64-bit) and has 12GB RAM with an i5 quad-core processor.
As I've indicated, only ONE of THREE websites on this server has this problem. Something is timing-out on the server when each page for this site is requested. The time-out takes about 15 seconds.
What I'm trying to figure out is how to determine what is timing-out.