Getting Error Message When Installing Plugins – Help Please!

Hello there,

I just installed WP version 3.0.5, but when I tried to update Akismet and NextGen Gallery plugins, I get the following message:

Upgrade Plugin

Downloading update from http://downloads.wordpress.org/plugin/nextgen-gallery.zip…

Unpacking the update…

Incompatible Archive. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature

Actions: Return to Plugins page

I received the exact same message when I tried to update both plugins. Can someone please tell me how I can get this resolved?

Thanks so much in advance,
Henry