A few posts about this one, can have a variety of fixes – in the instance I came across (environment : xenapp 6.5 servers, bare metal).
Seen this issue caused by a xenapp 6.5 to 6.5 farm migration. Post migration systems would hang from time to time, users couldn’t connect via ICA / RDP. A number of similar events to above recorded relating to different services.
Ultimately issue was resolved by migrating some missing policies that were missing.
Client drive redirection set to prohibited
Automatic inbox installation of drivers set to prohibited
auto client connect drives set to prohibited
client USB plug and plug device redirection set to prohibited
Issue was caused by an influx of usb / print drivers spilling onto the systems (urgh) – clearing them out and having the above policies got things back on track