Mar 20, 2007 12:43 AMfirstname.lastname@example.org|LINK
This problem of "SERVER APPLICATION UNAVAILABEL" is arises due to Application pools, If we run two applications of different versions of asp.net under the same application pools then this problem occurs,
The solution is to create a seprate application pool and then run the second website which is developed in another version of asp.net under that pool.
The website that JEFF given provides a complete description about creating a seprate pool.
Bye and Take Care