You can use a theme made for a lower OS but not for a higher OS. You can use a theme made for 4.5 if you're running 5.0. But you cannot use a theme made for 5.0 if you're using 4.5.
You'll find you need the base dimension zen them just as you need the base precision zen theme installed to use both 4.5 and 5.0 themes. Dimension for the 4.5 and precision for the 5.0. The base precision is now included with most 5.0 hybrids however the base dimension theme is not. You'll have to include it manually or install it separately. I did notice that the newest Nathanix hybrid does have the base dimension theme but it is in a separate directory and will have to be copied over for installation.
Seems the blackberry uses these themes as a template to go by with the custom themes. At least, that's been my experience anyways.
