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.
If you skip the Disable step, Windows will try to reinstall this device, and your issues will return without warning.
If you have crashes when hitting Play in POL on Vista, please try out the Windower 3.42.0 Beta.