I have never seen this error before (myself)
but it seems your mysql server is offline (so it couldnt connect)
all i can suggest is waiting and see if it comes back online or not.
also just something out of the blue, is your cpanel set to use paper_lantern ?
there has been odd errors and things since x10 updated the cpanel.
so its just a stab in the dark to check it and see.
and if it is not using paper_lantern, try switching to it.