Cannot automatically upgrade to version 2.9.2 or upgrade plugins

Hi,

I am trying to do an automatic upgrade from 2.9.1 to .2.9.2 on my wordpress.org site http://www.showbiz-i.com.

I never usually have any problems updating versions or plugins automatically but for some reason I get the following message:

Downloading update from http://wordpress.org/wordpress-2.9.2.zip.
Unpacking the update.
Incompatible archive: PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature
Installation Failed

I also get the message ‘plugin does not support header’ when I try to upgrade three plugins.
I basically downloaded the plugins to my mac and then unzipped them to upload as usual – but not working for me this time.

I have recently updated my theme to a pro theme by Theme Junkie but nothing else has changed so I’m confused as to what’s gone wrong? Changing this theme would not mess up the updates would it?

I’ve tried de-activating plugins and automatically upgrading but I get the same error message.

I not very savvy with all the technical side of wordpress, learning as I go!, so please explain in the most basic terms how I can solve my problems!! ;-))

Many Thanks

Kate