Lousy patches or cement?

Or knucklehead failure?

I've had three patches pffffffft out in two days on two different
tubes on the gf's bike. Delta brand patch kit. Same thorough prep as
always, a serious sanding, and no impatience with the cement--letting
it go fully matte and tacky.

Going to try again with another tube of cement from the auto parts
store that's tried and true--but it feels like amateur hour. Link to
pic below:

http://www.flickr.com/photos/landotter/7314251028/

It's pretty obvious where the patch bubbled up and the air snuck out
the side.

I've only used Park or Rema kits for years. Might or might not be a
connection.
.

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