In answer to the question in your latest post, create a php script and see if it can successfully create and write to a file within the plugins directory.
- The plugin manager should report problems if it encounters them. If it isn't, possibly a PHP error is occuring during its operation. Do you have access to PHP error log to see if that is the case.
- To operate the plugin manager requires php to have the zlib extension installed. Afaik, most distributions/web hosts do run php with this extension. You can check for it in your php by looking at the 'phpinfo()' output.
My plugin manager just says "Unable to download the plugin file: http://xxxx
....", and I might not be able to access to the PHP error log, because my site is on a free hosting. Actually I use 110mb.com as my server, and they usually have safe mode on. Could that be a reason too?