Class not found exception in Webi reports

HI Team,

when user tries to view a WEBI report, first we get Java version is out of Date, with options to Update, Block or Later.

When we select "Later" we get a JAVA error popup "ClassNotFoundException". com.sap.webi.ui.jrp.WebIAppletStartup. Please if any one could reply ASAP as it is highest priority.looking forward to your reply.

Thansk & regards,

Varun G.