I just bought a CIsco wireless router with built in VPN. It uses the Linksys QuickVPN client software to connect. I can connect to the VPN from other networks. However, when I am connected to my Novatel Wireless MiFi4510L hotspot, I cannot connect to the VPN.
I have never used Cisco's QuickVPN software or hardware but I do use Cisco's IPSec and SSL VPN clients on a regular basis. Both the IPSec and SSL clients work fine with my MiFi without any additional configuration.
Perhaps there are some tweaks to your QuickVPN client that can be made to better accomodate the MiFi. You will have to turn to Cisco for support in that area and more specific solutions. We really dont have many choices when it comes to configuring the MiFi to adapt to VPN's.
When I have issues connecting to my VPN's I normally try connecting in a few different ways after I confirm that the download speed is strong enough to support the tunnel. Typically a 1+ MB download MiFi connection will not give me any issues, any less then that and I tend to have problems. After I confirm the speed is good I try connecting to the Host IP Address instead of the Host URL (which is my default). For example instead of connecting to myVPN.myCompany.com I try to connect to 10.10.10.250.
You can also try moving around a little to see if your problem is location specific or not. Perhaps there is a conflict with one of the local towers that is not letting your VPN communication through.