Quote from: ID4 on February 14, 2015, 07:52:20 PM

I have tried cgminer with this string:

cgminer.exe -o stratum.btcguild.com:3333 -u dogie_U3 -p 123

result: No devices detected!

Same problem with the new U3 i got.

No one of my two purchased U3 was sealed originaly with the round adhesive dot. I can see remains of this Dot ( adhesive on the first Box and a half Dot on the second Box).
To seal the box for the new buyer they have used a narrow adhesive tape.
So i'm not the only one with this U3 problem.
Probably the U3 i've got from Amazon.de have done at least two rounds (Amazon > purchaser > Amazon > purchaser > now from me back to Amazon).

General problem with the U3 or just my problem becaue got no originaly sealed unit?

Its a hard one as it could be the unit or it could be generic environment problems that don't makse sense. And you won't really know this unless you repeat the procedure on another PC. Either way though, if you've purchased from a reseller then send it back.