Nokia 6030 Mobile Phone microphone appears not to work at times?

I have had my Nokia 6030 for 3 years without any problems. Several weeks ago I discovered that the microphone was not working (no one could hear me, but I could hear them - A ok.) I am not sure if the microphone is faulty OR is there a setting on the phone to mute the microphone - like a secrecy setting).

I have checked the battery but it checks out ok at 4+ volts. I being a bit technical have taken the phone apart and cleaned the connections and it now appears as though the microphone is now working - but I am not sure if this is only a temporary fix or not.

Any suggestions???? Many thanks in advance.