Unable to Connect after Installing Hotfix Rollup Pack 4 for Citrix Presentation Server 4.5

Cause
1. Legacy Virtual Channel drivers that use the Virtual Channel SDK are sending information two times to the server. During this condition, the server will refuse the connection.

2. Allow faster client disk access was manually set in the following registry hive:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\Wds\icawd]
"CongestionMonitoring"=dword:00000001

Resolution
1. Workaround to provide for 10.2 clients and above:
Add the following value into HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\WFClient
REG_SZ: AllowVirtualDriverExLegacy
Assign “FALSE” to it.

- Or -
Add AllowVirtualDriverExLegacy=FALSE to Default.ICA file in Web Interface.

2. Remove Congestion Monitoring from the registry.