The customized toolbar changes for the new toolbar and the changes to the
standard toolbar are kept in the same *.xlb file.
I'm changing my bet with this new info.
I'm betting that your change to the standard toolbar is really being saved ok.
But when you reopen excel, you have another workbook/addin that's resetting that
standard toolbar--deleting the changes you've made.
If you're interested in finding the workbook/addin that's doing the resetting,
you can do some detective work:
Chip Pearson has some notes on how to diagnose startup errors:
http://www.cpearson.com/excel/StartupErrors.htm
And Jan Karel Pieterse has more notes:
http://www.jkp-ads.com/Articles/StartupProblems.asp
Essentially, you'll turn off all the addins/startup workbooks and then open
excel. Make a change to the standard toolbar. And then turn on each addin
(closing and reopening) one at a time to find the culprit.