I have been setting up wired and wifi networks in trade shows for 10+ years now.
Welcome to wifi Hell :)

I do not think achieving 100% reliability is a sane goal in that context, but I found that there are simple ways to greatly improve the odds.

> Consumer-grade routers / AP are no good. They often do a fine job, and they always give up quickly.
In my view, using small-business equipment is a better way to go : still affordable, and a lot more resilient.
For about 400 $ you should be able to find a basic gateway and access point (new - I'm thinking sonicwall / netgear prosafe / hp pro curve...)
And if it matters, you still have web-based interfaces available to configure them.

> Use fixed ip when possible. Avoid encryption if you can, avoid wep if you can't.

> Reserve the network for your demo gear. If you also have to provide internet access to people working on the booth, use a separate network/gateway (your current linksys/d-link/... router might do the trick if less critical).

> Also : wired.
Not an option for your whole setup as I understand, but maybe part of it.

I am no sysadmin/network admin/whatever so this is basic stuff, but works for me on a regular basis in your exact predicament.
Hope this helps, and good luck to you.

In our help article we state that Dropbox employees aren't able to access user files. This is not an intentionally misleading statement -- it is enforced by technical access controls on our backend storage infrastructure as well as strict policy prohibitions. The contents of a file will never be accessed by a Dropbox employee without the user's permission. We can see, however, why people may have misinterpreted "Dropbox employees aren't able to access user files" as a statement about how Dropbox uses encryption, so we will change this article to use the clearer "Dropbox employees are prohibited from accessing user files".

Thread here : http://forums.dropbox.com/topic.php?id=36835

Poor choice of words indeed.