Since my broadband speed has been increased i have had some problems with the performance of my pc. After been connected for a while i suddenly loose the connection and the modem arrows in the notification area become red istead of green. When this happens i cannot open any other programs and when i try and restart the pc the only options i get is to switch user or go on stand-by. I have a voyager 105 modem supplied by plusnet.
see if this help
control panel/system/advanced then error reporting and disable error reporting. Often when you get an error it will dump the error to disk and hang the pc in the procces. If you can get to taskmanager you may see a service dumprep this is the problem you can kill the process to solve it.
If this stops it locking up you may then be able to see the modem errors