I'm not sure if you're talking about the SAME wifi connection issue I had (but is now resolved):
What I was running into was this:
As long as my 720 was used only for WiFi updating at my home wifi it was fine.
But once it had been used on more than one WiFi login (at my FBO) the problems began:
After that whether at home or FBO using wifi I could update TFRs and weather but anything big such as a sectional would result in starting to download, getting up to, say, 40%, then saying "retrying" and falling back to, say, 19% (or whatever), and never finishing. Had to do bigger updates via USB.
Ed sent me an update to the OPERATING SYSTEM which appears to have resolved that.
I suggest you call and if your syndrome is similar to mine investigate that option.
Hope that helps.
Alex