I tried to set up a Harmony 520 and started to get the "Unable to Display Content" straight after setting up my account. I initially thought it may have been my McAfee anti-virus or a firewall setting but turning these off made no difference. I then noticed a forum comment about special characters causing problems and I created a new account where my special question was now dogs name and not dog's name. The interface now works perfectly although I couldn't believe that this sort of bug could exist. I hope this is helpful.

I believe that many of the reported solutions to this error aren't really solutions at all. My experience tells me that many of these errors are caused by issues on Logitech's website. As folks hack-around trying to get things to work, the website starts working again and they think the last hack fixed the problem . . .

I actually went to the harmony remote website via internet explorer, and firefox(even though firefox isnt "supported yet") and got the unable to display content error directly from the website (not using their software browser). This is the string i got in the address bar when it gave me the error message.

[Link: members.harmonyremote.com]

notice,
ErrorType=VB Error ... XML document must have a top level element ... msxml6.dll

Quoting lchapman "the website starts working again and they thing the last hack fixed the problem" well if they expose the names of the dll's that they use they must be wanting to get hacked bad!!