plz help me in this problem

i have been installed FPGadv v 7.1 and it works fine one day but after that when i simulate any example like and_2 gate it was working fine in that day, even i put my license file in C:\Mtflexlm\bin\license.dat and creat it in my computer enviromentvariable and name, but now there is error in log window:

Generation completed successfully.
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Comparing HDL files with compiled files ...

Current working directory is C:/FPGAdvPersonal71LS/Hds/bin

Executing data preparation plug-in for ModelSim 5.8 - 6.1

Nothing to compile - design is up to date
Data preparation step completed, check transcript...
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Unable to checkout a license. Vsim is closing.
** Fatal: Invalid license environment. Application closing.
** Fatal: Licensing failure.

plz help me
and answer me here or @ my mail: ek4m2005@gmail.com
ek4m2005@yahoo.com