Some roundup of information on the breakdown of decorum on the House floor last night: First, a quick summary: on voting to add a measure to the 2008 agricultural funding bill that would have prohibited "illegal immigrants" from receiving some federal subsidies for employment and rental assistance, the (Democratic) chair closed down the vote, claiming to the failure of this measure, when it seemed (to some) as though the measure had already gained enough votes to pass. This disjunction caused considerable anger. Breitbart has a good extended video of what happened after the vote.

The Politico's summary:

The rancor erupted shortly before 11 p.m. as Rep. Michael R. McNulty (D-N.Y.) gaveled close the vote on a standard procedural measure with the outcome still in doubt.

Details remain fuzzy, but numerous Republicans argued afterward that they had secured a 215-213 win on their motion to bar undocumented immigrants from receiving any federal funds apportioned in the agricultural spending bill for employment or rental assistance. Democrats, however, argued the measure was deadlocked at 214-214 and failed, members and aides on both sides of the aisle said afterward.

One GOP aide saw McNulty gavel the vote to a close after receiving a signal from his leaders – but before reading the official tally. And votes continued to shift even after he closed the roll call - a strange development in itself.

CQ provides some more details:

The floor confusion arose when, with the tally tied at 214-214, two politically vulnerable Democrats, Nick Lampson of Texas and Harry E. Mitchell of Arizona, went to the well of the chamber to switch their votes to “no.” The buddy system would prevent Democrats who voted “no” from being targeted as the deciding vote in future campaign ads. Moments later, three Cuban-American Republicans from south Florida, Ileana Ros-Lehtinen, Lincoln Diaz-Balart and Mario Diaz-Balart, moved to change their votes to “aye.”

The five vote switches were called out by the House reading clerk. The two Democratic changes put the tally at 212-216. Ros-Lehtinen’s switch made it 213-215. Lincoln Diaz-Balart evened it at 214-214, but a tie vote fails. As the reading clerk called out Mario Diaz-Balart’s new vote, the Speaker Pro Tempore, Rep. Michael R. McNulty, D-N.Y., banged the gavel, apparently unaware that the second Diaz-Balart’s vote had yet to be counted.

McNulty had his eyes on the electronic scoreboard, which still read 214-214. But almost as soon as the gavel came down, the scoreboard registered Mario Diaz-Balart’s vote, pushing the tally to 215-213. The scoreboard showed those numbers and the word “FINAL.”

Within a minute or so, a flurry of post-gavel vote switches by Reps. Zach Space of Ohio, Kirsten Gillibrand of New York and Jerry McNerney of California — resulted in a 212-216 outcome.

It seems as though a lot of folks aren't blaming McNulty for this "meltdown." A number of outraged Republicans say that he was "trying to be fair" and did not "act in malice." Still, even as Deputy Minority Whip Cantor (R-VA) expresses his anger and some call this type of decision unprecedented, Minority Leader Boehner seems to be trying to reconcile things. CQ reports, though, that former Speaker Hastert (R-IL) was arguing very harshly with Majority Leader Hoyer (D-MD).
But to return to a paragraph from the Politico:

One GOP aide saw McNulty gavel the vote to a close after receiving a signal from his leaders – but before reading the official tally. And votes continued to shift even after he closed the roll call - a strange development in itself.

Is this GOP aide telling the truth? Who decided to give this signal? Was McNulty deliberately misled? Or did these "leaders" make an honest mistake? Or was no mistake made?
A number of Democrats ultimately voted in favor of this measure. How do they feel about it going down this way?

UPDATE 8/5: A select committee has been formed to investigate this disputed vote.