Hi,
"I tried to create a WEBI from launch pad , and I could create without some error", but "selected data source in Web Intelligence rich client 'client Document' An Internal error occured which calling 'initInstance' API .(Error:ERR_WIS_30270)(WIS 30270)"
I'd suggest you to apply SAP BO KB 1586166 - How to enable tracing for BI4.0 client applications to obtain more detail on the root cause of this 'initInstance' API error.
Hope this helps,
Jin-Chong