You will need to login to the router and export the certificate from the client vpn screen. Save it in the install directory of QuickVPN on the client pc.
If still you are getting problem try this
You need to use the openssl.exe app to get the certificate and save it into a file called cert.pem
Just do the following:
1) Open a dos prompt (Start -> Run -> cmd.exe)
2) Change to your linksys vpn client directory:
cd "C:\Program Files\Linksys\Linksys VPN Client"
3) Use the openssl.exe program (contained in that directory) to get the certificate from your server and save it into a file called "cert.pem"
.\openssl.exe s_client -showcerts -connect 10.10.10.10:443 > cert.pem
where "10.10.10.10" is the external IP address of your WRV54G router.
Note: for step 3, you might need to wait about 1 minute for the connection to your server to close.