Lua with Windows XP SP2 problems?

["Brett Bibby" <research@...>]

Hello,
Our game is using Lua for the PS2, GameCube and PC versions. Recently, 
Microsoft released a patch to XP called SP2 that has significant changes to 
the way security is handled. Since installing SP2, we have found that our 
game runs more slowly. Upon investigation, it runs slower because the game 
used to be consuming 99% of the CPU (as most games do on Windows using 
PeekMessage or other tight loops) and now it consumes 49% and Windows 
consumes the other 49%.

We have no idea yet while it runs more slowly, but I came across this 
tech-note:
http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/sp2mempr.mspx

First off, I'm no Windows expert because are focus is consoles and only 
using Windows for reference and testing. But in the note, it discusses that 
any allocated memory is marked in the "Data Execution Prevention (DEP)" as 
non-executable. It further cautions anybody doing JIT compilation and 
execution.  This got me thinking that our slowdown could be related to the 
DEP software checks on the Lua scripts we are running.

Has anybody else experienced Lua scripts that execute more slowly on Windows 
XP with SP2 installed?

Thanks,
Brett