Altera Modelsim

I have a very simple design in Quartus Web Pack ver 11.0 , and with it i have Modelsim-Altera Starter ver 6.6d. I get these error messages "vsim-19" when i do rtl-level simulation .

"failed to access library tb_xxx st tb_xxx"

I used the same vhdl files and run the simulation in Modelsim ver 6.2 SE and i see results as expected ???

I have checked the mapping of lib using vmap it is ok .

What is the problem ???

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