WW, this one is beyond me but:
If you followed the uninstall/ reinstall procedure given at Hearme, when you next joined a Hearme room, you should have been promted to accept the licence agreement and, on acceptance of this, the plugin should have downloaded and installed itself. Did this happen?
Do you have more than one browser with Hearme or run the standalone Hearme Voice Creator? Hearme do not document this in thier FAQ but the uninstall/ re-install procedure becomes more complex if you do. If, for example, you had Hearme on IE and later used Netscape, the IE plugin would be marked as uninstalled and would use the Netscape plugin. If you have more than one instance of Hearme, the only way I know of is to search for and remove all instances of EVP.dll and NPJac.dll, to remove the IE plugin as per the FAQ and to remove the registry entry as per the FAQ.
When a connection is made to Hearme, the text box is enabled and I can see no way that the type of modem will make any difference - you are either connected or not.
I can only see this one as being a problem with your set up - either the Hearme installation or a Windows issuse on your computer but:
1. Are you certain that you are clicking on the text box to make sure it has focus before typing? I hate asking this one but sometimes we can all be guilty of the most basic "pilot error".
2. Have you tried unchecking the embed text chat window before going into the Hearme rooms? I can't see why this would make a difference but unchecking that option will give you a button on the main screen to open a seperate chat box window.
3. Are you sure that you have been connected to Hearme on all your attempts to type? When you could hear others, you clearly were but assuming you have made a subsequent re-install and no one was around to listen too, it is possible that you did not notice that you were not connected.