This always happens to me. As soon as I reach out, I find a solution. I had to add the following to my web.config:
<system.web>
<httpRuntime requestPathInvalidCharacters="" requestValidationMode="2.0" />
<pages validateRequest="false" />
</system.web>
That part of my site is behaving correctly, now. Sorry for the bother but I hope this helps someone else in the future.
Thanks,
Dan