6700 not ring properly when call coming

[lengfengfly]

Hello everyone!
My UTstarcom is reflashed with WM6, En. I installed lots of software and removed some of them. Recent software include spb phone suite, FtouchSL, PlumSIP6, MalVal MVBklight, Webster Dictionary, magicall. I removed some of them and problem still exist.
The problem I will mention bothered me a year ago, after I reflashed the new ROM, it went away, but it come back again!!!
When sb. call me, I can see the screen be lighted and left-down corner shows "call status", on the top of the screen, a picked-up phone is shown. But it doesn't ring (if I set it as ring only) until 3~7 seconds later. If I set it as vibrate, it works fine.
What's the problem on earth?
I've worked with for days without any results.
I don't believe it has any relationship with signals. Don't let me try ##778 again, please.
Any superman can help?
Thanks!