oh, then you have other steps available you might take.
You might consider call your carrier and asking them to reset your voicemail, i am not sure what they do, remove and replace it on your account or something.
It has to be a software issue i have a Curve 8320 I have the same problem with sometimes the voicemail icon just staying there so if a 8310 has it AND my 8320 its got to be a software problem