OK, so it looks like the problem is with the <flow:executor>
element in your webflow config. Spring is complaining that it doesn't understand what that means, and it's probably because you're missing the namespace declaration in the config file. This looks something like this:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:flow="http://www.springframework.org/schema/webflow-config"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-config-1.0.xsd">
Your root element must look something like that. See documentation here.