I have been using Citrix application streaming for a long time. On my workstation I test different applications, so it suits me very well. I have been working away with out any real issues for well over a year.

Today however some strange things started happening. If you have used Citrix Presentation server before you may have experienced a situation when a server goes a little wonky and launches an application many times. I am not just taking about application freezing.

Today I experienced it with the streaming client. I was just working away with two streamed applications opened and a couple of local applications. Then out of nowhere the streaming client started to launch a number of different applications. I had about 13 applications open on me, 3 or 4 of each type. Very odd I thought. I terminated the XenApp streaming client and applications.

After a reboot, XenApp Streaming client started up a little message was displayed say it was reconnecting me to the applications. I thought this was very odd. I don’t see how you can reconnect to an application that is streamed and closed correctly.

I gave all the XenApp 5.0 servers a reboot just to make sure.

A few hours later the XenApp Streaming client started trying to re-authenticate me and failed. I rebooted once more and again the XenApp client reconnected me to the applications that I was not running before the reboot.

It seems like the client has got it self stuck on something.

I spent quite some time examine things. First I looked at the licensing state of the test farms I was using. One had expired its grace period as I had not pointed it at the license server yet.

I updated the license server to the latest version and downloaded a license file again. Still no luck.

So what was the cause of all my issues?

Yesterday I had enabled Trend Officescan’s Web Reputation service. There is a lot of Worm_downad going around at the moment and predictions of Worm_downad.kk coming on the 1st of April.

It was interfering with the PNAgent and XenApp Streaming client. It was causing intermittent communication between the clients and the XenApp servers. It was some how causing the streaming client to launch cached offline applications.

Disable the Web Reputation service and it works fine again. Adding the URL’s of the servers to the allowed list did not help.

So for now the Trend Web Reputation Service will need to stay off.

Something to investigate further maybe.