Check that your CICS® Transaction Server is working correctly, for example by looking at the CICS log. Insufficient storage on the CICS region may cause CICS Universal Client to hang.
To test whether CICS Universal Client has stopped responding, issue cicscli -l from the command line. If the call hangs then CICS Universal Client is not responding.
Try to reproduce the problem with tracing turned on. Take a client trace with as many components as possible active. As a minimum you need the API, DRV and CCL tracepoints; add TRN if possible. (Use wrapping trace if you do not want the trace file to get too large.) The summary trace shows whether the client or user application has stopped responding, and gives an indication as to whether the problem is in the client or server.