Reid - 1:19 am on May 11, 2006 (gmt 0)
If your pages are dropping or not being indexed then the number one thing before anything is to check that your site is not messing up googlebot.
Browsers are prety forgiving they can 'assume' when they are not sure and they can go into 'glitch mode' they can display pages fine even when they don't validate. But a bot is much more basic and if it hits an error it may just turn around and leave. It won't assume anything.
Check out your site with a lynx browser before you blame 'them' for anything.