Your line shouldn't have interleaving on - not at 8Mbps as there is simply no need. Interleaving is quite a complex task and I know from personal experience that the ST780WL which Be supply runs noticeably hotter the greater the interleaving depth. I guess that as with anything else, increasing complexity causes more failure modes.
Edit - your Linksys router has the AR7 chipset which Zen are complaining about so yes it's entirely possible that interleaving may be the issue.