SoapUI Test Case execution failure

I'm able to execute a test case in soap ui without issue but when I load it into load ui I get a class not found exception for one of the classes that I'm able to locate within the jar, so I know it exists. I've executed other test cases with other forms of driver and it works just fine. I'm able to import the class in the groovy script in soap UI, so I know it's not having a problem locating it in there.

The script is as follows (excuse the generalization, need to be within my confidentiality agreement) :

import org.openqa.selenium.WebDriver
import org.openqa.selenium.By
import org.openqa.selenium.htmlunit.HtmlUnitDriver

WebDriver driver = new HtmlUnitDriver(true);
driver.get("http://somewebsite.com")
driver.findElement(By.id("USER")).clear()
driver.findElement(By.id("USER")).sendKeys("some username")
driver.findElement(By.id("PASSWORD")).clear()
driver.findElement(By.id("PASSWORD")).sendKeys("some password")
return driver.getTitle()

The class it's missing is org.apache.commons.httpclient.protocol.ProtocolSocketFactory
I've verified that class doesn't exist elsewhere within any of the jars, so there are no overriding classes. It exists in one jar and one jar only. I'm at a loss as to what is going on, any help would be greatly appreciated.

If more info is needed I will gladly supply it. I'm within inches of getting this implemented at my company, potentially going to the pro version if it works