Some things will cause Windower to crash. One of the main causes is updates to FFXI breaking plugins and Windower.
After a patch, if your game crashes on load, please check the Windower News Forum for news from us.
Disable any broken plugin in init.txt until it is fixed.
A few things are known to cause windower to crash.
XFire - You can not use XFire with Windower & FFXI
Steam - You can not launch Windower with Steam
WindowsBlinds/AlienWare Skinning (Any 3rd Party windows skinning) - These will crash FFXI - Use uxtheme.dll hack or disable pol.exe from being skinned.
ProcessGuard - Will likely cause problems with windower - Thats what processguard is designed to do, stop windower from doing what it does.
Some virtual keyboards. (Like BizarroTrainer)
If you have crashes when hitting Play in POL on Vista, please try out the Windower 3.42.0 Beta.