Hi,
It may be , your java instance could be down.
If your java instance is not up and running, you may get Java Iview runtime error.
Please restart your java instance once again and try exporting it.
check this
[Refreshing the User Caches |http://help.sap.com/saphelp_nw70ehp1/helpdata/en/45/77e32308d072ace10000000a1553f7/frameset.htm]
Regrads,
Muralidhar
