Did you check to make sure the USB modem would be supported in Snow Leopard (please say yes)?
Snow Leopard/10.6 is a bug upgrade and a change in how the OS handles many things, including printing and software. PowerPC software now needs Rosetta to be installed to run correctly, Printers need their new 10.6 compatible drivers to work, and many third party items like USB dongles, like yours, need new 10.6 compatible software to be able to run now.
Now, here is an interesting thread
I found and read through. There are some things you 'could' try. That is you are handy with Terminal commands moving System files around.
There is also, on page 2 of that thread, a mention from a user who actually got it working in 10.6, but then it failed. He contacted Cricket and they said a fix is in the works, but no release date yet. Read the whole thread, 2 pages, and see if it is something you might want to try.
If Cricket does not have software drivers out yet for 10.6, then you are kind of out of luck here. The advice, beforehand, would be do not upgrade. Now, I am not sure what to tell you becaue it is too late. You may have to wait until they fix/release new software for your 10.6 to run that device correctly.