I got an issue when trying to open a modal popup when logged in to Sitecore
The site has just been setup in IIS, the server is running Windows Server 2008 R2 and it’s using Sitecore 7.2. The strange thing is that there’s another site that’s running under the same Sitecore version and the issue does not happen over there.
I got a clue after opening the ApplicationHost.config file on system32\inetsrv\config and it turns out that on the other site the UrlScan 3.1 was removed from the ISAPI Filters. After i do that the new site runs smoothly as well.