My 7650 has already been replaced by Nokia after it got the dreaded blue screen of death, (well, white screen of death)
Now, the replacement is dropping out mid call and then all I can hear is a quiet high pitched squeal from the earpeice. You press end and the phone locks, the screen slowly fading away to nothing and forced restart.
Only has happened on longer calls (about 8 or 10 mins i spose)
Also, bluetooth has stopped working properly...
I work at a mobile shop, and I can tell you these things, as great as they are, have big reliability issues. Nokia really have a terrible attitude toward this and other phones which have had too many problems. They swear this is the first one they ever had trouble with. Even the second time I report the problem it's the first time they've heard of it! They just deny everything...