I've had a problem with one live site (DNN 4.5.3).  I've recreated it on my local host. 

I'm using a modified DNN Gray skin, fixed width horizontal (basically a different logo and a background image.)

In IE7 when I click a menu item, I will get a quick indicator in the lower-left part of the browser window that as error has occured.  I managed to get this to stay on long enough to see the entire message:
Line: 53
Char: 1
Error: Object expected
URL: http://localhost/site name/directory/tabid/54/Default.aspx

The line and tabid numbers change depending on which item in the menu I click.

When checking this is Firefox, I will see an indicator in the lower-right corner of the browser that an error has occured in red letters, i.e. 1 Error, but that quickly goes away.  I was able to view this error just long enough to see this:
TABLE1_onclick is not defined
onclick(click clientX=0, clientY=0)

This is apparently located in Default.aspx, line 1.

Upgrading to DNN 4.6.2 is not an option as this client has already purchased - and the site is live - on an economy hosting plan at GoDaddy and GoDaddy doesn't offer/allow anything other than 4.5.3 for that plan.  However, I'm not having this difficulty with other 4.5.3 installations.

I'm at a loss as to where to begin.  Thanks for any ideas/direction for where to look.

I think I've found the problem. I'll post what I find.

Here's what it boiled down to: I got in a hurry with the skin for this site. And when it was late at night [laugh].

In my progress of developing skins, I've made it a habit to 'borrow' certain elements of one of my skins to use in another. Sometimes I will copy entire skins and give them new colors and images.

In this particular case, I borrowed a skin that had had more HTML coding in it than was needed for this site. I overlooked this code (like I said, late at night) and it looked fine when viewing only one page. It wasn't until I started adding pages and modules that this became an issue. I have since cleaned up the HTML and everything works fine.

I still don't know why IE7 and Firefox would only briefly display these errors, but frankly, I don't care [laugh].

Thanks for the info and well spotted, those small mistakes in code can sometimes take a long time to find!