Not sure if this could be related, but I had the same experience when attempting to import CA-signed certs in 7.5. After much time wasted, I found the root cause to be some missing Java jar files.
To fix the problem I downloaded the Apache Commons IO binaries and extracted the jar files to
C:\Program Files\HP\Systems Insight Manager\jboss\server\hpsim\lib
After restarting the HP SIM service, everything worked like a charm.