Modicon 340 communication problem

Gentlemen,
I have a Modicon 340 with a configured IP address and a laptop running Unity Pro through a VMware XP platform. I connected to the Modicon one day, didn't change anything and the next time I attempted to connect to the the PLC, I got an error message saying "This isn't a valid PLC address, or PLCis busy, or PLC is off." This has happened before but I don't remember how to fix it. Any help would be greatly appreciated. Thanks.

Can you ping it? I suppose with running a virtual machine, there is some chance the network config is altered... maybe was bridge, now NAT, or vice versa.. or whatever. Start with a ping and you can go from there.

You always have the option of the USB cable if you get physically close enough the processor to plug it in. At least this would help with verifying the configuration on the PLC end. Is this is a processor port on the CPU, NOE, NOC, NOR, PRA...?

Set Address

Try
PLC --- > Set Address tab ---- > Test Connection...

works for me .. Though I am using Windows 7