I am working as a VPN/firewall administrator for my company and I saw lots of problem with Linksys routers.
Funny thing is SMC router users doesn't report any problem at all.
Anyway please check these.
1.VPN client doesn't get along with Norton systemwork, software firewalls and Mcafee suite.
2.Open UDP 500 to your computer and enable IPSec pass- thru. You need to have static private IP address. Use either virtual server(SMC) or forwarding option (Linksys).
3.If this is too much for you, just put your computer into DMZ - I do believe you also need static private IP address as well.
4.If none of them works, replace Linksys router with whatever working brand. Don't spend too much time. Linksys should test the product before they sell. Also do not give hard time to IT techies in your company. they are not working for Linksys and we should not expect too many things from cheap routers. anyway
If you have extra money, buy netscreen 5XP or 5XT VPN/Firewall.
That is the best for SOHO as my experience and also web GUI is user friendly. You can even have site (home network) to site (company network) tunnel.