Problems when opening cursor for prepared statement twice

Hi all, i've the following problem: I declared a cursor for a prepared select (sums about two field, divided into groups over 4 fields). This cursor is used in function in the following way: OPEN q_cursor USING a,b,c,d,e,f,g FETCH q_cursor INTO x,y,z WHILE STATUS <> NOTFOUND calculate something FETCH q_cursor INTO x,y,z END WHILE CLOSE q_cursor The second call of the function gives the following result when opening the cursor (all calls are running within one transaction): -270: Cannot position within temporary table -101: File is not open What's happening ?? Greetings, Joerg