I know. it hasn't been updated since 2006, and therefore may be an abandoned project, but still. It is a fine looking instrument. Here's what seems to go wrong: When VUMeter is "watching" a device that is removed from the system (eg usb mics) and subsequently is started up, it fails terribly. There is no way to get it back up save putting the device back online and then starting VUmeter.
In this case I have a Zoom H2 recorder which is als a stereo usb mic. I use it to record directly into the pc, using VUMeter as a metering/monitoring device. Cool! When I unplug the H2 and exit the VUmeter (in any order), followed by restarting VUMeter, it is totally confused and some Windows error messages are thrown at me. Apparently it has "lost" its input and does not know where to go anymore. When the mic is put back on, VUMeter starts up fine again.
It would be nice if VUmeter were to recover from such a situation by selecting eg. the default recording device.
Examining the registry and the device list makes clear what goes wrong: the H2 was device #5 in the list and removing it shortens the list to 4 devices. VUMeter is now trying something with device #5, which no longer exists, and gets into trouble.