I think one can enroll oneself in two courses simultaneously if the courses are in open learning mode. Ignou B.Ed candidates are permitted to do any diploma course of 6 months, primary teachers who need both H.S. and d.ed/bridge course at a time. these two instances may not be directly relevant but may be helpful to find the answer.
Besides I personally know people who are enrolled in master degree as well as B.ed from NSOU at the same time.
I know my answer is different from my friend Pollo and so our new friend SOMNATH DAS will get confused. To help him as well as to gather better knowledge in this matter I invite my friends including Pollo to have more discussion in this matter.
As my knowledge goes, registration for two courses can not be done simultaneously. Nor is it permitted to register for another course before completion of current course. So, after M.Sc. result is published you may register your name for B.Ed. If you prefer to initiate B.Ed. course before completion of M.Sc., registration for M.Sc. may be made invalid.