Auto termination of sap sessions

Hi Experts,

When I am trying to display,change,attributes or download the document, normally a pop up screen used to come earlier and the document used to get displayed.But now I am facing a problem when i click on any of the above functionalities i.e., display,change,download now session is terminating as well as I am getting terminated automatically from other SAP systems also with out promting any message.

One more thing its only happening in my system,but when i login to other system with my user id i can display the documents.

Can any one help me on this? Have any one faced this kind of situation.

Thanks

Ratan