I am seeing this issue as well on my 8800, went through all the folders with missed calls and deleted them, 1x icon still wouldn't go away. Cingular wants to replace the device -- they couldn't figure out how to fix it. Since I have a ShieldZone skin installed I declined the offer unless they wanted to replace that too. Next option from Cingular "tech support" was to do a hard reset, which I haven't embarked on yet. Qutes on "tech support" are added because there is not much "tech" in their support. Very very poor on this issue.
7100g & 7210