If a link (ahref) has a target attribute and that target attribute's value is "_self", you get a "Window does not exist" Error when the command clickAndWait is run. After some research I modified the selenium-browserbot.js file in the method getWindowByName. I added the follow to the code

else if (!targetWindow && windowName == "_self"){ targetWindow = this.topWindow; }

So the whole method now looks like this

BrowserBot.prototype.getWindowByName = function(windowName, doNotModify) {
LOG.debug("getWindowByName(" + windowName + ")");
// First look in the map of opened windows
var targetWindow = this.openedWindows[windowName];
if (!targetWindow) { targetWindow = this.topWindow[windowName]; }
if (!targetWindow && windowName == "_blank") {
for (var winName in this.openedWindows) {
// _blank can match selenium_blank*, if it looks like it's OK (valid href, not closed)
if (/^selenium_blank/.test(winName)) {
targetWindow = this.openedWindows[winName];
var ok;
try {
if (!this._windowClosed(targetWindow)) { ok = targetWindow.location.href; }
} catch (e) {}
if (ok) break;
}
}
}
else if (!targetWindow && windowName == "_self"){ targetWindow = this.topWindow; } }
if (!targetWindow) { throw new SeleniumError("Window does not exist"); }
if (browserVersion.isHTA) {
try { targetWindow.location.href; } catch (e) { targetWindow = window.open("", targetWindow.name); this.openedWindows[targetWindow.name] = targetWindow; }
}
if (!doNotModify) { this._modifyWindow(targetWindow); }
return targetWindow;
};

I think this is the right thing to do, but am not 100% sure, it fixed my problem.

So to sum up if I see a target="_self" I set targetWindow to this.topWindow.

Craig