::Can you see what I might be doing wrong?

Some ideas:

If you're specifying the table width, you'll want to make sure the sum of all cell widths are equal to the table width.

Also, try putting something in each cell, even if it's only a non-breaking space ( )

Try fiddling with the resultant HTML in a text editor (or FrontPage, if you have it). It sounds like a browser rendering issue, not a .NET coding issue.

HTH