Alright guys, it seems that this is mostly an issue with Windows Vista and Windows 7, only 10-20% of the people with issues are on XP. This also applies to a wide range of machines(even on the latest and greatest machines available).
Basically, Windows Vista and 7 LOVE to throw things into the page file, especially when an Application takes more than 10% of the physical RAM available. I ran Windows 7 and was seeing 25-10,000 Page File hits per second while playing(with up to 25,000 during loading). This didn't cause much of an issue on either of my machines, because my main drives are not where Killing Floor is installed, and they are faster drives that are fully defragged.
For machines running Windows Vista or Windows 7(with 3+ GB of RAM), it seems that turning off the Page File safely fixes long loads.
For all other machines, especially those with 1-2 GB of RAM, it would be unsafe/unnecessary to turn off the Page File. The best that can be done is to use a good defrag tool(such as MyDefrag or Ultimate Defrag) to try make sure the page file and Killing Floor's files are not spread out across the hard disk.
Also, make sure that your Anti-Virus is not scanning every file Killing Floor loads before allowing Killing Floor to access the file. This can be done by adding an exception for the Killing Floor directory into your Anti-Virus.
Also, in an issue that appears to be similar, some players have also improved load times and game performance by disabling their second monitor.
Please let us know which, if any, of these suggestions helps you. Also, if none of these help you, please tell us that, post your system specs, and let us know everything you've tried to do to fix the issue.