TCL errors generated by Exchange HTTP Persist iRule

We have a pair of Big IP 3900s with the Edge Gateway services. I understand this is not the full LTM solution but we are still using the basic for a Round Robin connection back to Exchange. In addition to EWS and Autodiscover not functioning at all via the Virtual Server, I have noticed in some instances very poor performance for clients using RPC over HTTP. Also the Outlook Web App can stall when trying to load.

F5 Professional Services did the install of the F5 units and everything appeared fine until we went into a production and noticed that EWS, a function that Macs and Out of Office Replies use, fails to work. Because we don't have the full LTM product as part of Edge Gateway we weren't able to use the Exchange iApp as you would normally do in this instance. He had to copy the iRule over from DevCentral and I believe there might be something not quite right with it. As the majority of my experience and training is related to APM I was hoping someone could point me in the right direction.

Attached is the iRule as it exists on the F5.

TCL Error:

Nov 1 15:21:07 tmm3 err tmm3[11466]: 01220001:3: TCL error: /Common/ir_Excchange_combined_http_persist - Failed on current side. invoked from within "NTLM::disable"

If connections aren't being maintained at one server or the other once a user connects it's very possible this would be the source of my headaches. Thanks for your help!