--- gui.tcl.old	2009-01-09 22:12:15.000000000 +0400
+++ gui.tcl	2009-01-09 22:14:52.000000000 +0400
@@ -832,7 +832,7 @@
 		set oldgrab ""
 		if { $modal } {
 			set oldgrab [grab current]
-			grab set $w
+			catch {grab set $w}
 		}
 
 		tkwait variable customMessageBoxAnswerTracker($uniqueId)