To find the open circuit voltage between C and D, can I assume that no current flows through the current source between A and B. If it does not, the Thevenin voltage is 10V. But since it is not an ideal current source some current should flow through it. Also, to find the short circuit current V_x = 0 (short circuit between C and D). So should the current source be not considered while calculating the short circuit current. If so I will get the short circuit current as 1mA. But this analysis does not seem to be correct because it is independent of the current source.