when using the Network Device Monitor, can I have it generate a text file when it detects a problem?
You can have alerts run an external program or VB script. I assume you are able to pass parameters in the "Program to execute" string, including using variables. Create (or get a script guru to create for you) a .bat file or a VB file that creates a text file for you, using the passed parameters for filling in useful information.
(Someone who is using that feature may like to confirm or deny the ability to pass parameters when executing external programs or VB scripts.)