modelsim ase in multi-user environment

Thanks for the responses, bit of a Doh! moment here. Turned out that one of the environments that we were using had $MODELSIM set to the root of our installation /altera/11.0/modelsim_ase

Interestingly it wasn't preventing the initialisation stages from finding modelsim.ini file as shown in the original post...

# Copying /altera/11.0/modelsim_ase/linux/../modelsim.ini to /altera/11.0/modelsim_ase

but it was causing the error messages regarding write access and a number of other oddities for example the following error message when attempting to create a new project. On entering a project name in the popup we would get the following error message

Invalide (sic) Configurtation/Project file suffix ""

Further confusion was added by the fact that the ase version has 2 different splash screens depending on whether it is being run for the first time or not thus leading us to think we had subtly different versions installed. The title bar is also different if you start vsim from the command line or from within quartus->tools->run eda simulation tool->rtl level simulation. The path to the executable is the same in all cases.