The default condition for SOCKS acceleration is auto, which means that if the destination TCP port is recognized as an application, it is accelerated. If the destination TCP port of the application is 5101, Yahoo IM, then the default setting is to treat the SOCKS traffic as Yahoo IM. SGOS does this as it is trying to accelerate the SOCKS traffic. This KB article provides instructions for disabling this behavior in CPL, thus targeting the solution to the applications affected rather than the entire proxy.
If a well-known destination TCP port is being used by a SOCKS based application, then the default behavior is to accelerate the traffic (that is, stop treating the traffic as SOCKS and treat the traffic as if it were coming into the proxy on the destination TCP port).
Add a rule in a web access layer that tests for the destination TCP port being the port in question and have an action of socks.accelerate(no):