Reference number brackets wrapping to next line in Word 2007's bibliography

If you don't want to change the XSL style as explained in M. Dudley's answer (which simply did not work for me), you can simply change the column width by hovering next to the citation number column, then dragging it to the right when you get the cursor:

Note that you really need to change this column, and not the margins at the top ruler—otherwise you'll shift the entire bibliography to the right.

This appears to be a defect in the IEEE 2006 style when you have long URLs in a citation.

One of my citations has a long URL that is just about the same width as the page. It forced the citation column to be wider, and squished the reference number column.

I edited that citation's URL to have a space so that the URL could wrap. Now it doesn't squish the reference number column.

I did try editing the citation style XSL file (C:\Program Files (x86)\Microsoft Office\Office12\Bibliography\Style\IEEE2006OfficeOnline.xsl). I replaced <xsl:value-of select="'1%'"/> with <xsl:value-of select="'5%'"/>. However this did not help because of the above problem with the long URL.