WordPress Plugin API error during installation
When I was logged into WP (2.8.5) and I tried to install a new plugin (from the dashboard), I would get the following error:
“An Unexpected HTTP Error occured during the API request.”
Basically, according to WP user efree_unix,
The cause of error is too long in the process of requesting the API plugin in the wordpress server so that the operation timed out. By default, wordpress give 5 seconds time limit to request a plugin. If within 5 seconds does not get a replay, then the process will be stopped and displayed an error “An Unexpected HTTP error occurred during the API request.”
THE SOLUTION:
Open wp_include/http.php file on line 223
‘timeout’ => apply_filters( ‘http_request_timeout’, 5),
change the script above into
‘timeout’ => apply_filters( ‘http_request_timeout’, 30),
You may refer to efree_unix's post at here. At least it works for me 
LikeWordPress plugin upgrade failed: solved by Core Control
I have been using WordPress 2.7.1 for a few months. In the very beginning of the first two months, I was able to upgrade the plugin, with some chances of failure. But lately, I was totally unable to upgrade the plugin in WordPress through built-in FTP. It just failed miserably, with the message: Download failed.: name lookup timed out.
Plugin upgrade failed
As this problem has been happening with the chance of 100%, I suspect that this might be the problem from Web Host side, probably caused by incorrect setup or configuration. Until today I googled the problem, I eventually found a working solution, thanks and redirect by CarltonBale to WordPress Trac.
Here is the detailed solution of mine:
- Download Core Control plugin (version 0.8 as of 3th August '09)
- Install Core Control plugin from Plugins > Add New
- Go to Core Control Settings page. Enable HTTP Access Module.
- "External HTTP Access" fore will come out. Go to the page.
- Under Manage Transport, choose "Test Transport" for cURL.
- If it return the result: name lookup timed out, then disable the cURL transport.
Final look of core control settings
And finally, plugins updates is working. Going to reduce the growing number beside Plugins tab 