Recently I had some grief trying to allow non administrator / power users from using the Citrix web ICA client. Whenever the connection to the presentation server would happen, the connection would timeout with no error message.
After scouring the internet, I found an article where the system admin decided to make all users using Citrix a member of the Power Users group.
Thankfully, the solution of why the error was occurring was there too. Apparently you need write-access to the MSLicensing key for all users.
Once we did this through group policy, all of the users could connect succesfully to the Citrix applications. Hurrah!
The full key path is: