40GB for 500,000 documents in a db with 1 view seems REALLY large...  do these docs have attached files?

I've only had to restart http for design changes when working in SCXD  - Single Copy Xpages Design...  

Are you using a template?  If not you should.  Rather then restarting http you could also try to clean it and rebuild it.  Maybe Build Automatically is off...  or on and not working that well due to the document count.

The best practice is to design off a local template and refresh your demo app when making changes.

I don't think it is related to the size of the database, though the usual reason for the failure to update is an error in the code as XPages will return the last good page. So I don't have an answer other than if in doubt keep the admin client open and tell http restart generally does the job. It is frustrating when it happens, because I have found that it is pretty inconsistent and I can waste a lot of time looking for errors when there are not any.

I would try to do a Project/Clean which generally fixes these sorts of issues.

Thanks for the quick replies. I tried to do both clean and build and all that kind of stuff. It didn't help. The code had no errors, and Designer built the pages without any problems. I also checked the files right on the server and it had the latest code there, too. It's really annoying when these things happen silently, because I am not looking at the latest code in my browser and when that happens, there's no point of developing. For me as, Bill said, too, the only solution is "restart task http" from the console.

I have gone for a considerable time without having the problem, then it jumps up and bites my butt, then goes away. One thing that I have noticed is that XPages does not like it when all the XPages Design is not signed by the same ID, but even with that it does not complain all the time.

That is a good point.  XPages really does want everything in the app to be signed by the same ID.

On an action button on an XPage that I was testing I added a bunch of print statements and when I clicked the button the action ran, but none of the print statements executed (there are no errors in any of the source). So next I added a line of code that had an obvious error in it and ran it again. The action did not pick up the error. I have signed the DB both with my ID and the server ID to no effect, likewise I have tell http restart, closed both the browser and designer and Notes and still to no effect. This is really weird. I have had this happen in the past but normally resigning the DB solves the problem. So Casba you are not alone. Oh by the way I also restarted the Domino Server.

Just did a full shutdown and restart of the server, closed Notes and Designer, signed the DB now the changes are working. Go figure!