<p>I've found an issue with ASP.NET that I know at least has stumped one other person out there.  We were trying to use an HttpModule to handle wildcard 
requests to a web application.  The generated url is dynamic and could 
potentially be several hundred characters long.  Unfortunately there 
appears to be a limitation in the aspnet_isapi.dll file that limits 
the length of the path in the url to MAX_PATH which is hardcoded at 
260 chars. </p>

<p>Has anyone else ran into this and found a way around this limit? 
Query string parameters are not an option. </p>

<p>Thanks, 
Greg Ballard</p>

The problem actually lies within Windows, not ASP.NET.  Windows has set MAX_PATH at 260 and when IIS takes a request for a longer filename, it will fail.  You've probably found is this KBase article already, but for anyone else:
http://support.microsoft.com/kb/q177665/
.  The Applies To: Section shows this is expected behavior from NT 3.51 all the way to Vista and Server 2003.
As for a workaround, I had a similar situation, but we would up abandoning our attempts to avoid a query string parameter and did it anyway.