http://www.tuaw.com/2008/10/10/sprint-smartview-for-macs-bricks-broadband-cards/
TUAW reader John T. alerted us to an issue with Sprint's SmartView application, version 1.85.0007.0. SmartView for Mac is a recently released (August 28, 2008) application which is used with Sprint's Mobile Broadband cards and USB modems.
The issue, which occurs with the ExpressCard cards used with MacBook Pro notebooks running Leopard, causes the card to stop working. To get the card working again, it's necessary to reinstall an older version of the SprintView software or previous software such as Sierra Wireless Watcher.
This problem does not occur when using the Sprint Mobile Broadband USB connectors such as the Sierra Wireless 595U, Sierra Wireless Compass 597, or Ovation U727. John noted that Sprint's tech support team is aware of the issue, but that the faulty software is still available on the download page.