Standard Arabic words can't begin with two consonants

Only if they're marking vowels, which they usually don't. ;) I really need to learn Arabic some day.

and it seems the Iraqi dialect doesn't pronounce the u.

I wonder if they devoice the vowel as the Japanese do in some environments: cf. desu ka being pronounced /dEska/. In Classical Arabic, is ghurayb 'raven' pronounced with the u as /u/ or /@/ (as in tutor or but)?