Portal ESS leave overview internal error code: 0x2101

Dear,

in ESS, leave overview or create leave request, ITS version, Portal 6.0, SAP 4.6c ... For Portal ESS errors, some times we get that error in ESS i-views:

“The Internet Transaction Server failed to generate the response for current request, please contact the system administrator, internal error code: 0x2101”, any comments? how to fix this error? its keep randomly repeated ..

thanks

Abdulrahman