Hello,
ModelSim PE Student Edition 10.4a license has expired and I have 
re-installed it by downloading again the software + new license. Since I 
did that I am not able not compile my vhdl files anymore. I get the 
following error message:
** Error: (vcom-66) Execution of vlib failed. Please check the error log 
for more details.

When I type "verror 66" for more information, it says:
# common Message # 66:
# The execution of the executable mentioned in the error message failed. 
Please check if the expected arguments were being passed to the 
executable.

Before the license expired my vhdl files were compiling without errors.
Does anybody know which can be the route cause for this error?

Thank you in advance!
Amalia

Is there more information the message log before this error appears?

This error is very general and often you get warnings or useful 
information during compilation or when starting the simulation that can 
help us narrow down the root cause.