If you have an OG reading that low, I would keg the Beer, force carbonate at 8psi and let it age at least a week at cold temperatures. If you are bottling, add 4oz of dextrose to the 5gal. batch, stir well and then bottle and let age 3-4 days at fermentation temperatures and then refrigerate. Make sure everything is 'clean'.
BTW, what was your starting OG reading. For a Hefeweizen I would start at a starting OG of 1.046-1.050 and end with 1.016-1.018. Yours, IMO, is too low for a Hefeweizen.
A Hefeweizen taste is also affected by the fermentation temperature. Between 70-75F, it will have more of a 'banana' flavor. Between 65 - 69, it will have a more 'cloves' flavor. I would not recommend fermenting a Hefeweizen below 65F.
I used Liberty Hops before on a Hefeweizen, but I only used 1oz for a 5 gallon batch and it came out pretty good after only 3 weeks from brew to finish. Using 2oz of Liberty may lend to a more bitter taste with a 60 minute boil.
From what you have said, I would say the amount of hops used and the fermentation temperature would lend to a 'sour' flavor. Since I don't know the starting OG, I cannot say if OG is a culprit, but it could be. Let it age and re-sample every week. It will get better, but be patient.