Anonymous block performing much worse then separated statements

I two statements that when are executed separately, a truncate and an insert - they run in seconds.
When put in an anonymous block, they take more than 20 minutes and begin to throw errors.
Does anyone have any explanation for this?

the block looks something like this -
BEGIN       TRUNCATE_TABLE('WANDH_HR');       INSERT INTO WANDH_HR(EMPLID,STATE,CREATE_TS,MAINT_TS)         (SELECT             A.EMPLID             ,'NJ' As "STATE"

            ,'12-Jul-2011' As "CREATE_TS"

            ,'12-Jul-2011' As "MAINT_TS"

        FROM             (

                .


        .

        .etc., 

        .

        .


 

END; Doug Cowles

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