I bought my vypyr in march, and it's worked fine since then. But now when I turn it on despite everything looking fine it produces no sound and just buzzes.

cable could be broken.
Also open up your guitar and check to make sure none of the solder connections are loose.
100w Peavey Valveking Head
Mesa Rectifier 4x12 Standard Cab
Ibanez RG 321
Boss DD-7
iSP Decimator x2
BBE Boosta Grande
Modded Crybaby
MXR Blue Box
Numark Power Conditioner
Korg DTR-1000
The Vypyr forum is a lot better for this sort of problem. They have more technicians that know the vpypr unit and its technical problems.
A Good Place To Start: http://forums.peavey.com/viewforum.php?f=33
Ultimate Guitar Set Up Q&A Thread─┤
are you positive its the amp? have you checked the cable? a different guitar?
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Gibson Faded Flying V
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Quote by freedoms_stain
I can't imagine anything worse than shagging to Mark Knopfler.

Maybe shagging Mark Knopfler, but that's about it.
Try turning it on without the cable plugged in, then plug in the cable while the lights are cycling. See if that makes a difference.