Technically vim exposes the x11 clipboards (plural) as registers - I never use registers, but I think

  "+p

[Ed: for those not familiar with vim: " can be thought of as 'with/from/into register named:', + is the register and p is paste. Similarily "+yw is 'yank/copy current word into register named +' ]

should be paste x11 selection. I don't normally use gvim/vim as an x11 application, but looks like * (star) is typically system clipboard:

http://vim.wikia.com/wiki/Accessing_the_system_clipboard