I need help with my regular check out

[Guest]

everything seems ok but after i add item to normal cart it shows me my shipping options and then when i click continue it just keeps refreshing the page leaving no way to finish the checkout....with google checkout i got it working good i just want to know if anyone can help me with making GC use weights to calculate shipping instead of fixed shipping.....my website is www.CheapNFastMD.com and you can try with any item i will cancel any order that you may make by accident trying to help me