Ok found the solution!, Go into Joomsef and manage sef url's, select "don't sef" to the checkout url's, done, hope this helps people, and see if you find a solution to an answer this is what you should do btw.

Hi, I know this thread is old but i'm having the exact same error that with JoomSef enabled it will not let me proceed to complete an order with Virtuemart it keeps redirecting back to select shipping method, I'm amazed the amount of threads and an answer wasn't given, the people who had this problem over a year ago surely found a solution, any help would be great, it seems like a problem that no1 was able to answer