Hi, I'm running the latest MIUI (1.5.13) and I'm getting quite worried about my phone. When I try to make a call I can hear nothing through the speaker and (i've been told) I can't be heard on the other end. A factory reset/cache wipe fixes this problem UNTIL I reboot my phone, at which point I have no sound through the speaker again. Can anybody please suggest what might have gone wrong and how to fix this please?! Thanks!