The Windows Forms components are not localized through assembly resource strings of your solution, but rather through resource strings that are compiled with Infragistics DLLs themselves. See the online documentation on how to localize resource strings.
-Matt
You need to translate any string you want. Look here for an example:
http://help.infragistics.com/Help/NetAdvantage/NET/2007.3/CLR2.0/html/Win_Customizing_Assembly_Resource_Strings.html
Strings list is here:
http://help.infragistics.com/Help/NetAdvantage/NET/2007.3/CLR2.0/html/Win_Assembly_Resource_Strings.html
If you don't want to do it one by one as the first article suggested, here is what I did:
1. Add a resource named GridResource and copied all strings from the second article and translated what I needed.
2. I used this method as LocalizeControl<GridResource>(Infragistics.Win.UltraWinGrid.Resources.Customizer)
{
}