make sure the case-mounted speaker is connected properly -- it will beep error codes if it detects an error, but of course you can't hear it if the speaker isn't hooked up. usually a blinking power LED indicates sleep mode...
have you tried unplugging it from the wall for a while and plugging it back in?
as a last resort, i'd take it apart and put it back together again
that often works for me (seriously..it could use the cleaning too)