QB Pro Timer could be used under Ubuntu. You need to install few libraries for it, since this piece of "software" written on VB.

It uses MDAC, OLE automation, MS JET for handling database and bunch of other activex components.

In order to make life easier, I installed 'winetricks':

$ wget http://www.kegel.com/wine/winetricks

Next, install required "tricks" in order to run QuickBooks Pro Timer:

$ winetricks vb6run mdac28 native_mdac mfc40 jet40 native_oleaut32

That's it. Now you can proceed as usual with installing QB Pro Timer and use it.