The LCD Controller (TCON) board is a likely suspect, but a Main board problem can also cause these symptoms.
I would begin by replacing the TCON board which is not an overly expensive component.
Here is a link to all the parts available from ShopJimmy for your set:
http://www.shopjimmy.com/vizio-va320m
And here is a link to an LCD Controller (TCON) board currently available on Ebay for $50 US:
http://www.ebay.com/itm/VIZIO-VA320M-LCD-CONTROLLER-BOARD-6870C-0266A-/370498121667?pt=LH_DefaultDomain_0&hash=item564368afc3
If the TCON board replacement does not clear up the problem, then the problem likely on the main board which is significantly more expensive and much harder to find. You will have to seriously weigh the cost benefits of spending any more time / money trying to repair an inferior quality set with probable main board issues, versus putting those resources towards purchasing a brand new, higher quality set (like a SONY) which would obviously come with a full warranty.
Please comment back here to this page if you have any details to add, have any questions, have difficulty accessing the links, or just require further general assistance and I will respond as soon as I see it.
I hope that was helpful to you, good luck and take care.
Joe.