Saw on another newsgroup that someone had this error  occur with SQL 2000
(related to MSXML extensions). They upgraded to SQL 2005 and it cleared it up.
Is there anything in the event log  around the same timeframe that might narrow
it down? Any errors related to MSXML?

We are currently running SQL 2005..
Here is something from the application event log  right at the time the full
crawl is scheduled..Maybe you can make something of it...

Event Type: Error
Event Source: Office SharePoint Server
Event Category: Office Server Shared Services
Event ID: 6482
Date: 11/6/2007
Time: 12:00:15 AM
User: N/A
Computer: B2BCHEROKEE02
Description:
Application Server Administration job failed for service instance
Microsoft.Office.Server.Search.Administration.SearchServiceInstance
(65c18932-2c77-4774-aa39-342ef2ed9fc5).

Reason: A transport-level error  has occurred when sending the request to the
server. (provider: TCP Provider, error: 0 - An existing connection was forcibly
closed by the remote host.)

Techinal Support Details:
System.Data.SqlClient.SqlException: A transport-level error has occurred when
sending the request to the server. (provider: TCP Provider, error: 0 - An
existing connection was forcibly closed by the remote host.)
at
Microsoft.Office.Server.Search.Administration.SearchServiceInstance.SynchronizeD\
efaultContentSource(IDictionary applications)
at
Microsoft.Office.Server.Search.Administration.SearchServiceInstance.Synchronize(\
)
at
Microsoft.Office.Server.Administration.ApplicationServerJob.ProvisionLocalShared\
ServiceInstances(Boolean isAdministrationServiceJob)

Any ideas?

In addition, it seems to crawl  the SSP admin site  and the MySite host just fine,
but not the main  portal..

That makes me wonder about whether (a) your alternate access mappings
are set properly, or, probably more likely, (b) whether the content
source start addresses and the crawl  settings are correct. Just a
shot in the dark. Go to your shared services administration, click on
search settings, content  sources, and see what the entries under
"Local Office SharePoint Server sites" look like.

I will do that..thanks for the response..
I happened across this blog entry and read it..I also did an iisreset, and the
crawl worked the way it was supposed to and I was able to get meaningful search
results..
But I assume that soon, it will stop working again..
Here is the blog I found..
forums.microsoft.com/.../ShowPost.aspx