This post is copied almost word for word from a discussion on the T-Mobile support forums with the original answer supplied by Chris Dobson – FIXED! Web’n’ Walk III stick (Huawei E170) for Mac OS X Snow Leopard. I have copied it here as content on forums has a nasty habit of disappearing, and have tweaked it in a couple of places. I can confirm it works with my Web ‘n’ Walk III stick on my 2011 Macbook Pro with Mac OS X 10.6.7 . Now over to Chris…
I’ve finally found a fix for using your Web’n’ Walk Stick in Snow Leopard. It’s a bit long winded but I’ll try and explain as best I can, but it will do until there is an official fix. Make sure your dongle is not plugged in when you start. Please be aware that t-mobile is not responsible if you mess something up, I am just a customer offering advice. Also you need to be running the 32-bit kernel mode for this to work.
Note: You can check if you are running in 32 or 64 bit mode by clicking the Apple logo on the top left of the menu bar, then More Info…, then Software. If the line “64-bit Kernel and Extensions” says “Yes” you are in 64bit mode, if it says “No” you are in 32bit mode. To change to 32 bit mode, you need to power on your Mac while holding down the 3 and 2 keys. To change to 64 bit mode hold down 6 and 4 during power on.
Download: www.t-mobile.at/officetogoSW/MM_2_0_3.dmg
Double click on the white ‘drive’ icon that will appear on your desktop and look for the package called ‘MM 2.0.3 Intel… Right click this software package and choose ‘show package contents’. Navigate to contents>resources and then double click the file named HuaweiDataCardDriver(2.6)…. Then proceed to install this as you would with any other software.
Plug in your dongle, and you will be prompted to enter the ‘Network Preferences’ utility’. You now have an item added to the list on the left called ‘Huawei Mobile” Click on this to configure it.
Add *99# into the box where it says Telephone Number
Tick the checkbox to show modem status in the menu bar (handy for easy connection)
Hit Apply to save these settings.
With any luck, you should now be able to connect using this new connection you’ve created.