I had nearly similar profile with 4 rejections(every time the reason was: Your proposed studies.........):
i had applied in sheridan and seneca college for PSSCN computer system technician and computer networking and technical support.
my ielts bands were:
L-8.5 W-5.5 S- 5.5 R- 6.0 Overall-6.5 earlier{L-8.5 W-6.5 S- 6.5 R- 6.5 Overall-7 at present}
10th-----76% ICSE
12th----- 55% non-medical (PSEB)
the reason for your rejection is that you have chosen computers field after non medical,according to me you should opt mechanical,electronics or any other engineering field but not computers because it is not regarded equal to engineering in canada(it is a different disciple).Also your computers marks should be added to your final result in 12th not simply as grade.
Do not waste your time and money by applying again really quick,you should definitely change your program and strongly state in SOP that why you have earlier choosen computers and why are now choosing different field.