When testing Appeon I created a new web site called Appeon Web Site with physical address %SystemDrive%\inetpub_appeon\ to avoid mixing Appeon projects with other projects in my computer and had no problems with this configuration. The http port will be different though (e.g. 8001 or 8008).
I also noticed that trying to access named instances of SQL Server didn't work (e.g. ServerName: SERVER\DEV). I had to specify the specific port the named instance was using (e.g. ServerName: SERVER, Port: 60306).
My 2 cents.