Idera SQL Check: idling in transaction (dangerous)

I am using the freeware SQL Check app from Idera, and in the processes window, I have some SPIDs with big fat red balls with blue centers. According to the legend, these are connections that are idling in transaction, and they are dangerous. I unfortunately don't really know what that means, or how to go about resolving the problem. It seems to be the same 3 users every time I open the program, and one of those 3 processes is the account VMware ESX 3.x uses to connect to the database.This is on SQL 2000 SP4 Standard Edition.