Don't know. You will need to post issues with Sellenium in the Sellenium forum.

Try it without all of the unnecesary code:

$url = "http://tut.by/"
[Reflection.Assembly]::LoadFrom("d:\_Instalation\PowerShell\Selenium_PowerShell_eXtensions\selenium-dotnet-2.44.0\net40\WebDriver.dll")
$ie = New-Object OpenQA.Selenium.IE.InternetExplorerDriver
$ie.Navigate().GoToUrl($url)
# check for page errors before accessing page
$html=$ie.PageSource

2015_02_22 : powershell version
2015_01_09 : http://lh4.ggpht.com/-4vGpquxJ8Ok/VLAXQuRhZUI/AAAAAAAAKLg/OMnJ_936J_U/s0/img9c0e84ff6d47711c6cf9c1eba46f1d08.jpg
2015_02_22 : I perform script in powershell ise

$url = "http://tut.by/"
[Reflection.Assembly]::LoadFrom("d:\_Instalation\PowerShell\Selenium_PowerShell_eXtensions\selenium-dotnet-2.44.0\net40\WebDriver.dll")
Start-Sleep -Seconds 2
$global:ie = New-Object OpenQA.Selenium.IE.InternetExplorerDriver
Start-Sleep -Seconds 2
$global:ie.Navigate().GoToUrl($url)
Start-Sleep -Seconds 40                     
$html = $global:ie.PageSource

2015_02_22 : If I press F10 and perform script in debug mode all is right
2015_02_22 : If I press F5 and play script without debug mode then
2015_02_22 : in result $html = $null  
2015_02_22 : Why script do not work right without debug mode?