Recently, i started to get "Error running Unnamed: Address localhost:8080 is already in use" errors when starting tomcat through intellij. I checked netstat and nothing was using port 8080, restarting the computer didnt help. Interestingly, i could start tomcat from the command line on port 8080.
The same day, ESET NOD32 3.0.684.0 Antivirus was pushed on my box. It was the evil problem. I needed to disable the following things in it in order to get tomcat to launch again:
Setup -> Advanced -> Web Access Protection -> Uncheck "enable web access protection"
Setup -> Advanced -> Web Access Protection -> HTTP -> Web Browsers -> put [x] on java.exe and idea.exe
apply and reboot.