Locks up on incoming calls and takes very long time to dial during speed dial

[ionCPB5]

For quite a while now, my PPC 6700 locks up on incoming calls to the point where all I can do is watch the incoming call displayed and wait for it to display the notification that I missed a call. It won't recognise and actions I try whether to answer or to ignore the call.

Also, when dialing, especially during speed dial, it takes quite a few seconds before it starts dialing.
Is there anything I can do about either of these issues. Very frustrating, any help appreciated.