Problems running ModelSim from Xilinx ISE

Not sure if it helps but Mentor's Supportnet newsletter had this today:

Symptoms

You have more than one simulator loaded, or have replaced an existing one with
another.
The Xilinx compiled libraries are not valid for the simulation. The default
information in the modelsim.ini file are not correct.

Causes

The Xilinx project accesses ModelSim from 3 different places, and if they don't
all point to the same install problems can arise.

Solution

Check that the following all point to the same install:

1) Environment path (check that only one path points to the modelsim
executables), remove all others. You should have one valid path (Xilinx uses it
to create the default modelsim.ini file using "vmap -c".
2) Xilinx top Menu: Edit --> Preferences -- ISE General -- Integrated Tools --
Model Tech Simulator: Example: :\\win32pe\modelsim.exe
3) Window "View": M Simuilation; highlight the device in the Hierarchy window.
Expand Design Utilities and Right Mouse Button 'Compile HDL Simulation
Libraries' and select 'Process Properties': fill in the GUI as needed.