I can't see the sub-nodes under SAP Systems after starting the J2EE engine

I installed the SAP J2EE engine last week and it worked well. Today as I start the J2EE engine and as I click the node SAP Systems to open the sub nodes, it takes a while and at the end nothing comes up, i.g. I can't see the sub nodes such as C11 and the engine name.

Somebody can help?