Reader Ext. error ALC-RES-001-002

I'm getting this error frequently when running on the clutsered instances and have to restart the LC server to make it woring again (even with super admin role granted). any idea? also, what's the minimum rights required for Reader Ext. web apps to read templates from its repository? the version is LC ES update1.

[11/16/09 15:10:12:747 EST] 0000003c CredentialsHe E com.adobe.livecycle.readerextensions.CredentialsHelper findCredential ALC-RES-001-002: No credential found with alias [PCG-LC-READERCERT].