Google's system doesn't recognize some "newer" browsers. When you download the app you'll notice it says "Download Google Maps 2.1.0 on your Blackberry 40" (or something similar.) You'll need to change the download link. If you copy the link address and change the "40" in the link to "42" (there are two instances in the link) you'll get the right download for your device and you'll get the right icon and possibly everything else will function for you.
There are also issues with OS 4.5 on BES 4.1.3 and some 4.1.4 where permissions can't be set properly.
Code for 4.0 devices (I assume)
Code for 4.1 devices (I assume)
Code for 4.2 and up devices (I assume)