Colin,   Unfortunately this is by design of the VPN software disabling any other local network traffic, even virtual.  I've heard of similar concerns when having local network resources that you want access to while you are also connected through VPN and this being disabled.  This is a common secure configuration for corporate VPN traffic.  Your best bet would be to discuss with EMC IT if there is a way to enable split tunneling for this purpose.  However typically split tunneling is frowned upon due to the potential security vulnerabilities that opens you up for. 
Free VMware Player with Isilon simulator on EMC laptop. (OneFS 7.0.2 first - others later). Excellent install/run write-up!  Using VPN to EMC (for training & email). Simultaneous local access to Isilon simulator not working.  Shutdown VPN, simulator access through WebUI is fine. Any solution to have VPN active while working with OneFS simulator under VMware Player?  Thanks! (colin)
Use EMC VPN same time as Isilon Simulator?