This really is a techsupport issue.
3 things cause this
#1 mods
#2 corrupt install
#3 MTU too high for you internet connection
you say you have no mods, you say you have re-installed
so delete the HoN settings folder in MyDocuments and try again
otherwise if you are sure the install isn't corrupted you need to test what MTU is best for your connection and tweak it down
either way, not a HoN bug denied