do i have a dodgy plug socket?

[a66as]

When ever i try to turn my switch of at the mains it makes a spark noise, once i kept it on overnight and my mobos light kept going off and on, also today my monitor screen kept going blank and on again, whats going on

should i switch it to a different socket?

 

[a66as]

could damp be causing it? my wallpapers have sort of developed black lines so i think i may have a damp problem, either way i got another two mains sockets in my room ill switch ot over to them