Well that day, we had a citrix server whose published apps when launch would crash wfshell.exe. Initially, we suspected it to be printer drivers, so I removed all the printer drivers from the citrix server and tried launching apps again. No luck, wfshell.exe still crashes.
After almost one day of checking for knowledgebase, it turns out that a previous installation of oracle client reduced the path variable for the citrix path to shortcut names. For example, c:\program files\citrix became c:\progra~1\citrix instead. This does not work well for wfshell.exe.
After reverting the paths back to c:\program files\citrix… , we managed to get the published apps running again.