Cller can't hear me when i turn on speaker phone?

[gravelsandwich]

Anybody have a resolve for this?
When I make a call or receive a call I will turn on the speaker phone. initially it works fine but as soon as the screen dulls (you know how after about 30 seconds the screen dulls before it turns off) the person on the other end can't hear me but I can hear them. Has anybody got a fix for this?
Cheers