The Telegraph says certain 'sources' say the President was too tired not to snub the British Prime Minister.
Sources close to the White House say Mr Obama and his staff have been "overwhelmed" by the economic meltdown and have voiced concerns that the new president is not getting enough rest.

British officials, meanwhile, admit that the White House and US State Department staff were utterly bemused by complaints that the Prime Minister should have been granted full-blown press conference and a formal dinner, as has been customary. They concede that Obama aides seemed unfamiliar with the expectations that surround a major visit by a British prime minister.

But Washington figures with access to Mr Obama's inner circle explained the slight by saying that those high up in the administration have had little time to deal with international matters, let alone the diplomatic niceties of the special relationship.
...
The real views of many in Obama administration were laid bare by a State Department official involved in planning the Brown visit, who reacted with fury when questioned by The Sunday Telegraph about why the event was so low-key.

The official dismissed any notion of the special relationship, saying: "There's nothing special about Britain. You're just the same as the other 190 countries in the world. You shouldn't expect special treatment." The apparent lack of attention to detail by the Obama administration is indicative of what many believe to be Mr Obama's determination to do too much too quickly.
For a guy that campaigned on 'restoring our alliances', using diplomacy to solve all the world's problems and all that, this is especially pathetic.

Bush didn't pull this kind of stunt (iirc) and his appointments, save for Harriet Miers, certainly went over better.

CR