The excellent Charles at Mercury Rising summarizes:

Some of the formal elements of the complaint:
1. Partiality of the election institute (IFE) in not stopping the "Swiftboating" ads

2. Manipulation of the preliminary count by IFE

3. IFE failing to mention 2.5 million votes in the preliminary count.

4. Use of patronage, including some heavy-handed pressure on elderly/ill/disabled recipients of social programs including Vivienda Rural and Adultos Mayores.

If I understand aright, 152 complaints have been filed outside of District 15. 151 are directed toward inconsistencies in calculation and precinct "irregularities" like the pregnant urn, which have already brought 52,000 votes into question. For Mexico City, there were "generic irregularities," presumably polling stations closed by flooding, voters told ballots were waterlogged, and so on. District 15's results were a litany of irregularities.

The complaint also alleges that the software and computer system were compromised in a manner that would allow tampering. The 904, 604 blank ballots are 116,447 greater than in 2000 and are 2.16% of the total. In certain unmonitored districts, there are suspicious statistics for the Nueva Alianza candidate.

And, says Charles, they've got videos.

A guy in blue dumping ballots into an urn. Maybe we can track that sucker down...