I had the same issue but got around it by opening ACAD 2011 and then right clicking the icon when it shows up on the taskbar. "Pin this program to task bar" option shows up there.
I tried that too, and thought it worked, but it is the mechanical icon, and it opens mechanical, even though you pinned it from plain old Autocad.
Wish Autodesk would help?!?!?!?
I don't have Mechanical and only use ACAD 2011 alone so I'm not sure I can be of any help. Have you tried editing the path and program name on the taskbar shortcut? The shortcuts themselves are located here on my PC...
C:\Users\\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar
I tried a quick test and right clicked the ACAD shortcut, selected properties and changed the target path to launch a different program (had to type it in by hand though). I was even able to change the ACAD icon. It worked for me but I think my set up is much more simplified and you may have already tried this. Good luck!
Another alternative is to set a key sequence to open it up. If you have a shortcut that opens plain AutoCAD go in to properties and set a key sequence to open it. I use Ctrl+Alt+F8.
OK....I know I can do that, but why should I have to?
How about if Autodesk just FIXES what they totally messed up in the first place?
This is the worst release yet. Don't get me started, A-desk....., read the posts
Go into your c:/program fies/autodesk (or wherever you have vanilla installed) and find "acad.exe". Pin that to the taskbar.
It is not a Autodesk issue it is a Windows issue in how it handles shortcuts.