I am running Firebird 1.5.2 on a brand new Windows 2003 server. Dual
3.6 GHz processors. 2GB ram. Dual channel mirrored raid array. I am
testing this system at the moment and am the only user.

Executing the same query repeatedly yields vastly different results.
Sometimes the return is virtually instantaneous. Sometimes it takes
over a minute. Windows performance monitor shows practically 0%
processor utilization and 0% disk utilization during the time the
query is apparently executing.

Any guesses as to what might be causing this?

The database file name ends with .fdb and volume shadowing is turned
off. Connect string = localhost:e:\truckload\transeaz.fdb