I have a WSS v3 server with SP1 and i was looking at upgrading the search to MS search express 2008.
So i taught let me upgrade it to SP2.
Donwloaded the trouble and then installed it and it went like a breeze.
Everything went ok only i didn't test whether the search was working(MY FAULT

-trusted MS)
After a while i got an email from a user saying search isn't working.And i taught i'll just restart the search service and it will be fine.But that didn't do the trick
Look a the ULS logs and Event Viewer and found lots of troubles liek below:):
The start address <sts3://myserver/contentdbid={6a68a5ab-2b97-419f-9e88-57875d494f39}> cannot be crawled.
Context: Application 'Search index file on the search server', Catalog 'Search'
Details:
The object was not found. (0x80041201)
After doing some research i found its a common error with different solutions but nothing specific.
Funny enough the search was working before installing SP2
So the error didn't make sense to me at first.
See similar errors
here
Later i came across :
Method 1 :Disabling the loopBack check
Method 2 : Specify Hostnames
And you will have to do this in the registry See how to do it
here
But tried all that but still no LUCK
So i taught maybe i should look at my default content access accts and the search acct. But they all have access to the database.
Also did a fullcrawl from the command line but nothing.
Later started looking at the AAM(Alternate Access Mapping) maybe somethings had changed but all remained the same.
I later found Ivans post
here about AAM's and i must say its a MUST READ.
But after going through that i didn't find anything that could solve my problem.
I also came across this
post by MVPs and one person reckons you might have to re-install WSS
I now taught of looking at site collections and subsites to make sure all the access is OK etc
After i checked the root site http://myserver:PORTNUMBER and bingo i got a http 404 error which means the site wasn't exisitng thats why it couldn't start the crawl at the root address.
So i wenu to the Sharepoint Central Admin > App Management > Create Site Collection and created a blank team site on the root site.
And bingo it worked like a charm
Hope this helps.