Thanks for the effort, unfortunately there are two problems with your solution:
1) Instead of choosing Background, you need to choose Buttons, then proceed according to your instructions. This is a minor problem, and if this fix worked, then all would be fine.
2) The buttons on the old toolbar (at least on the bitmap you provided) are arranged in a different order than on the new toolbar.
For example, the 6.31 "DCC Options" icon is replaced with a Stopwatch (which should be for Online Timer), and the "Notify List" icon is replaced with the old "DCC Options" icon. Other icons are similarly re-arranged. This is obviously a MAJOR problem, and the results (icons that don't match their functions) are worse than the new 6.31 icons.
Can anybody else help?