Unit conversion tools not working?

[tenforty]

Hello!
I just received my HP Prime and the first thing I've been trying to figure out is the unit conversions. I use shift+Units and the first time it opened I was able to access the Tools tab but every subsequent time I am only able to access Units and Const. I am pressing the Tools tab but it just exits the units menus when I do that, as if I've presses a blank tab button. Grrr!!! it's driving me crazy since unit conversions are something I need to do all the time. What am I doing wrong? Have I somehow locked out the Tools tab? It's not in exam mode and the first time I was able to get to the tab (or maybe it opened there?) but now I cant.

Any help would be appreciated.

Thanks!
Bruce