This is old news, but I just discovered it today.
Apparently WinDbg !locks command is broken in the last stand-alone release of Debugging Tools for Windows. To fix the issue you need to download the WDK or downgrade to the previous version (6.10).
Found via http://www.voyce.com/index.php/2009/06/03/windbg-locks-command-broken/ while trying to track down a deadlock. I forgot how fun crash analysis can be . I say that both seriously and sarcastically at the same time. When your tools are broken it can lead to hours of wasted time. 🙁
Personal note for later lookup: MS Symbol server path (for easy pasting):
Dump any spare symbols you need in temp (not a best practice!)