Problems with updates

To whom it may concern,

My site doesn't seem to be able to update. On the updates page iI have this error message "An automated WordPress update has failed to complete - please attempt the update again now." when I click to do so, it does nothing.

Also, I have four plugins that need updating including three WPMU Dev ones. However, when I try and update them the site goes into maintenance mode and when it comes out of it, they are not updated.

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