Heads Up :
The post you are writing will appear in a public forum. Please ensure all content is appropriate for public consumption. Review the employee guidelines for the community here.
For some reason my virtual Cisco VPN adapter in the Network Connections became stuck in disabled mode. I had to manually re-enable it and then reconnect - that worked for me.
The problem is that you are not completing the path to the file you want to boot from - you need to a forward slash after flash:/ - this is the sequence:enconf tboot system flash:/c3560c405-universalk9npe-mz.122-55.EX3/c3500c405-universalk9npe-mz.122...
