"RSS Error: WP HTTP Error: Couldn't resolve host 'www.remarpro.com'"

I’m getting this error when I try to update my plugins, although now all plugins are listed as up to date, so I’m not sure if the update really did work or not…

I also get this error when I try to update core:

Download failed.: Couldn’t resolve host ‘www.remarpro.com’

Installation Failed”

(Though again, it seems to have updated me to 3.8 in spite of the error msg…)

And this error when I try to search for/install new plugins:

An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. If you continue to have problems, please try the support forums.

I tried reinstalling the wp-includes folder, but that didn’t solve the problem.

One thing to note: the site is hosted on Yahoo! Small Business (not my choice), which has caused problems for me in the past – such as the inability to use permalinks or contact forms. I’m looking to move my client to a new host, but in the meantime would like to fix these new issues (which only just began recently) if possible.

Many thanks in advance for your help.