It appears that the issue was related to the upload testing. I initially got the error again when I ran the upload test by itself but afer I cleared my cookies/cache files in Firefox, I no longer get the error.
The last several times I've run the combined test, everything seems fine until it gets to the very end to show the results. I get the followng screen:
Request-URI Too Long
The requested URL's length exceeds the capacity limit for this server.