I think it was an error related to the second cluster node. I closed the second node and no such problem. And workbench is really faster now 🙂
But i have another error. I followed your suggestions regarding "renderPDfform".
[8/18/08 18:09:22:003 EEST] 0000014a FormServer E com.adobe.formServer.FormServer dumpLog xmldata: XML document structures must start and end within the same entity., cause: XML document structures must start and end within the same entity.