GMail is an internet based email system, so it sounds like the problem lies with the program that you are using to copy messages to your computer. My guess is that it's only copying new, unread messages, so if you check the messages on your phone first it won't copy those messages because it doesn't see them as "new."

You should check your settings and see if there is a way to just copy all messages.

Regardless, you should always be able to log into the gmail.com and see all of the messages (unless you've deleted them).

 

If you were to go in and do a factory reset from the menus, you'd get all of your google calendars, and all of your contacts back in a few minutes. All of your google stuff (data, not programs) only sort of resides on your phone, it backs up to your google account.

The only thing you'd really lose are your SMS/MMS messages, which you can get apps that back that stuff up for you.

 

Us a client like thunderbird setup with imap and gmail and you won't have any issues with wondering where email is or isn't. Thunderbird 2.0 - Gmail Help

I have this setup on all my PC's, win or linux, and no matter what PC I'm at, or on the Droid, what's in my folders is on each system, changes are universal.

J.

 

If your home computer is using a client to access Gmail via POP or IMAP, be careful, because if you have any rules/filters that move messages into folders other than you Inbox, it will download the message from Gmail and when it's moved, delete them from Gmail.

The Gmail app on the Droid only views what you'd see in your Gmail account if you accessed it with a browser.

I had my mail client on my Mac accessing Gmail, and had some filters... some emails would get filtered into folders on my Mac, and were gone from Gmail online or on my phone. I simply stopped using my mail client on the Mac to access it.

 

You can set up GMail to filter and have messages skip the inbox and go straight to a folder (or label, as Gmail calls them). Then you don't have to worry about messages being deleted.