if the UK and the US had been watching the alleged airline bomb plot for months

why did the ban on liquids happen so suddenly and in the middle of the night

Maybe they didn't know the planned method of attack until then?

Supposedly they were investigating [link|http://www.csmonitor.com/2006/0816/p01s02-wosc.html|flows of money donated for earthquake relief in Pakistan] and that somehow put them on the trail of the alleged bombers.

if the alleged attack was 'imminent'

why weren't any weapons or explosives found

AFAIK, they were going to use common household chemicals, e.g., [link|http://www.npr.org/templates/story/story.php?storyId=5632570|acetone + hydrogen peroxide], so they wouldn't need to have them around (they could just pick them up at the local QuickieMart on the way to the airport). Why would they have needed weapons?

if the investigation was so well done

why was one 'suspect' released almost immediately without charges

Sometimes bystanders are picked up when they're at the wrong place at the wrong time. In the USA, too often it seems that people in that situation end up behind bars for far longer when the T-word is invoked. :-(

if this alleged plot was a UK thing

why was the National Guard called out in CA and MA

I don't know about California, but Boston was one of the destinations and [link|http://www.newsmax.com/archives/articles/2006/8/10/94715.shtml?s=lh|Romney activated the Guard to help with Logan Airport security]. I wouldn't be surprised if it was an over-reaction by a governor who is apparently running for president, but I don't know.

It's very easy to get wrapped up in the moment and take everything from the security services at face value. (I'm not accusing you of that.) But it's also easy to take every missing piece of information as being indicative of shoddy work or incompetence or even a conspiracy. (I'm not accusing you of that either ;-) Healthy skepticism is certainly called for, but let's see what - if anything - the people in the UK are charged with.

My $0.02.

Cheers,
Scott.