I upgraded to 4.4.5 this past week and ran into a bug that I was told was template related. When IE PC users check out, they input their address info and it hangs when trying to add it. Then you get an error telling you to refresh and same thing happens again. I had 4 customer complaints today and I was able to reproduce the issue myself in IE.
There was another post here with a fix, but it did not work for me and was told it was probably the template:
http://forum.x-cart.com/showpost.php?p=335472&postcount=58
Also get the error on the Terms of Service and Privacy links, which I have not been able to get to load even in 4.4.4 and I put the wording in both the language files and the actual privacy and tos pages in x-cart. Again, I was told it had to be template related.
I have not added any mods to the store yet, so it can't be a mod conflict issue.