Newbie: Lost page rank of 6 to a 0 white bar..robot.txt file was missing

Hi ..I'm in desperate need for some help. Today I noticed a big drop in sign-ups to my webpage. Looked in google and I had dropped significantly and my toolbar showed a white bar. Some page still had some page rank but most had gone white. Looking at the logs all I could see was that google bot had visited but it was giving errors at first. then I looked and the robot.txt file was missing somehow from my server. I could of swore it was there before. Does anyone know why my page might have lost it's page rank and if it will come back?

Thanks In advance!!

If robots.txt is not present, it tells the bots everything can be crawled. It's to exclude files from being crawled, so I really don't think this is the cause.

It may be cold comfort, but the forums are currently overflowing with plaints from site owners who have seen catastrophic falls, with going from 6 to 0 not uncommon.

While there may be some deep, underlying cause, were it me I'd screw my courage to the sticking place and wait it out for a week or two, to see if things stabilize, before pressing the red button. G has many times before gone topsy turvy for a week or two, then righted the ship.