I'm using Selenium IDE 1.8.1 with Firefox 14 on Windows 7.

I see this exception:

[error] Unexpected Exception: fileName -> chrome://selenium-ide/content/selenium-core/scripts/selenium-browserbot.js,
lineNumber -> 228
when running the following:

<tr>
    <td>assertElementPresent</td>
    <td>//a[text()='! selenium test customer']</td>
    <td></td>
</tr>
<tr>
    <td>clickAndWait</td>
    <td>//a[text()='! selenium test customer']</td>
    <td></td>
</tr>

As you can see the element is present (otherwise the assert would fail halting the
test), so I can't figure out what's going wrong.  It seems to only occur if I run the
test at the fastest speed. If I slow it down, the error doesn't occur. That's not really
a solution though, as running the entire suite at half speed is way too slow.