Problems with calls hanging up

[Acarin]

I have one of the first Droids that came out, and i love it, but I've been having a wierd issue lately. It did several updates about a month back and since then ive been having problems with calls. The problem occurs when I'm on a call. When already on a call, if someone else calls in and i just let it ring so it will go to voicemail, when they hang up, it hangs up the person im still talking to as well. Also, if i push the red button on the right that pops up when someone else is calling in while im on the phone, and slide it to the left it hangs up on the person im on the phone with as well. Does anyone know what might be causing this, or how to fix it, or if an app exists to fix this problem, its really starting to get irritating, and it didnt do this before. Thanks for any help anyone can give.