Workflow failing on start(retrying) - Sharepoint Custom Workflow Error

I had created a workflow for a client that just sends an email when an item is added to a Custom List. Depending on a field that was added, it would send to a different user.  Simple enough!  Started up Sharepoint Designer and created said workflow.  Added an item to the list and BAM:  "Workflow failing on start(retrying)". After recreating it several times and changing Token Strings within the XML, the problem still remained. So...

After battling with this issue for the past few days I finally found a solution.  First I went into my Sharepoint logs at: c:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\LOGS\ . I ran a dos command  

"type [LogPath/MostRecentLogFileName] | findstr /i /r workflow >> c:\moss_errors.txt"

What this does is output any line in the error log which contains the string "workflow".  This lead me straight to the culprit: "Engine RunWorkflo

w: System.Security.SecurityException: Request failed. at System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Assembly asm, PermissionSet granted, PermissionSet refused, RuntimeMethodHandle rmh, SecurityAction action, Object demand, IPermission permThatFailed) [...]"

So on an so forth...  Did a quick google search for that error and stumbled across a lovely post in this thread: http://social.msdn.microsoft.com/forums/en-US/sharepointworkflow/thread/20fd2a72-13e5-4310-a06b-3ded6e7d370e/?prof=required that stated that their Nintex Workflow 2007 program stopped behaving correctly after installing Citrix XenApp.  It did something to their "shared.dll" that allowed it to be uneditable... or so they thought.

On a whim, I decided to google "Citrix XenApp Web Interface for Microsoft Sharepoint" and I found this thread: http://connect.nintex.com/forums/thread/423.aspx which gave me the direct solution on how to fix things

Unfortunately it has recently come to our attention that the file shared.dll is being deployed erroneously to the following location:
C:\Inetpub\wwwroot\wss\VirtualDirectories\\bin

The work around is very simple, just delete the dll from this location and your workflows will function as intended. 

Perfect!  and there you have it.  Just drill down to said directly -- port was the domain name on my server, and move that file to a backup location or recycle bin and then try your workflow out. I recreated mine just to be sure.  Likely it should work if the error was due to the Citrix App.  Also make sure to make this change on all domains and servers if youre in a farm.