Oracle 10g Privileges revoked

I have a sql2005 server connected to oracl开发者_运维知识库e 10g , the account on the sql is given privileges to access certain tables. Intermittently the Oracle privileges get revoked.. Oracle DBA tells me that he had not revoked the permissions (I tend to believe him).. Is there a way to figure what is going on..

One possibility: if the schema owner were to drop and re-create a table, any privileges on it would disappear and need to be re-granted.