What's interesting here is that following the A test positive, the B tests performed in a lab in Gent were "inconclusive". The B samples have now been re-tested at the the French national anti-doping laboratory (LNDD) in Chatenay-Malabry. This lab is the focus of the Landis appeal - as far as I can tell not on the basis that the test results were wrong, but on procedural grounds - so i can see this one run and run. For my views on why EPO tests can be hard to interpret see my posting on EPO and EPO testing.
There are enough procedural uncertainties here that this story is very likely to run and run, particularly if Mayo is suspended or banned as a consequence. It's not good that these cases get prolonged while the protagonists argue the toss over procedural irregularities. Athletes have a capacity to lie over their guilt for a long time before evidence forces them to come clean - see for example the sad story of Birillo.
21/12/07 update - cyclingnews.com reports Mayo's belief in a conspiracy!
22/12/07 update - Apparently the Spanish Federation are refusing to sanction Mayo. I told you this one would run and run! The line they are taking is that the UCI are interpreting the rulebook to suit themselves rather than the rider or the sport. Presumably this is connected with the UCI's belief that the first attempt at a B-test was inconclusive rather than negative.
23/12/07 update - still running! Apparently the UCI will refer the Spanish federation's stance to CAS. The machinations of CAS, however, seem to take forever, so it may be some time before this issue is resolved.