May be because
1)You will have an IS Service called in the page u r trying to open in MWS and not given the correct wsclient-endpointAddress,username or password(Implicit Environment variables basically).
2)The Service which you are calling might be in an infinite loop,or taking more time to respond.Just try increasing wsclient-socketTimeout.
3)Your IS will not be started.
If you still need clarity about this just open the show details button and see what exactly the error is…!
#MWS-CAF-Task-Engine#webMethods#webMethods-BPMS