While there are loads of reasons why this can happen, I identified an odd one that, hopefully, will help you if you an encounter an IPConfig hang.
Scenario and solution:
1. Start a Viftual PC 2007 Virtual Machine running MOSS 2007 w/SQL Server 2005 on Windows Server 2003 SP2.
2. Open a command prompt and type IPConfig.
3. IPConfig hangs.
4. Break-out of the hung IPConfig command or open a new command window.
5. type net stop mssqlserver
6. type net start mssqlserver
This resolves the IPConfig hang error and is probably related to a timing issue on boot. There is probably a more elegant solution, but this will get your TCP/IP protocol stack functional again.
Technically Speaking author, Ethan Wilansky