Nokia recently released a software update for the Lumia 900 that addressed the connection issues many users were reporting. So many users, in fact, that Nokia also offered $100 credit (the total cost of the device on a contract) to Lumia 900 owners.
If you have yet to update your Lumia 900, the process is easy; you just need a bit of time and access to a computer with an Internet connection.
Install the software and finish the setup process, then connect your Lumia 900 via USB to your computer.
If you are using Windows, once your Lumia 900 is connected to your computer, the Zune software will automatically check if there are any updates available. If an update is found, you can begin the update process by clicking on Update Now. The Zune program will let you know when the update is finished. Your device will display a screen similar to that above and may even restart a few times during the update; this is normal. It is very important you do not disconnect the device from your computer until the update is done.
If you're on a Mac, with the Windows Phone 7 Conncetor app running and your Lumia 900 connected, you will see an Install Updates button present if a software update is found. However, in my case, the device alerted me that an update was available, while the app did not. To force the app to look for an update, click on Device Options and then Check for Update.
Once the update is found, you will be guided through the update process. As with the Windows approach, it's very important you leave the Lumia 900 plugged in for the duration of the update process. Unplugging a device early will have dire consequences for the device and your mental health.
The entire process should take less than 15 minutes, depending on the speed of your Internet connection (required to download the update and software). If you run into any issues, Nokia has set up a support page offering help to Lumia 900 users.