DNS problem

[#1]

This evening I'm having a problem connecting to 2 sites - both my own web sites
1) http://www.ipgphotography.com/
2) http://paulgulliver.co.uk/
Using chrome browser I get  Error 137 (net::ERR_NAME_RESOLUTION_FAILED): Unknown error. and with IE9 I get "dns server may be experiencing problems"
The fault seems only to be with these 2 sites, hosted by different companies (Zenfolio and Go-Daddy), with the Go-Daddy site I can access via ftp without any problem
Both sites are also unavailable via my tablet - both laptop and tablet uses the same router so could this be a router problem. I've tried switching the router off for a while and re-starting  with no effect.
Both sites were ok last night.
Any ideas what the problem might be?
Paul

[#2]

I have just checked both your sites at
http://www.downforeveryoneorjustme.com/
http://www.websitedown.info/
They both report that your websites are down for everyone, probably best to contact your hosting companies
Regards
Mike

[#3]

neither work for me with either pn/opendns or google servers

[#4]

This could be the cause? (For the GoDaddy site anyway)
Alex

[#5]

Ok, thanks for the replies, strange coincidence that both site are down. I hadn't come across that report for the Go-Daddy site. I'll contact Zenfolio about the other problem.
Paul
Ahh - I think I've just realised the  connection here, the ipgphotography domain is registered with Go-daddy and re-directed to Zenfolio, so the Go-daddy problem is affecting both.
At least its not my end, that was my biggest worry