Quartus 11.0 编译FFT ip核出现以下错误，这是啥原因?上网搜了一下，有人说是因为没有付费的原因。我下了一个IP核的license，但是编译还是会出现一下问题
Error: Node instance "asj_fft_sglstream_fft_110_inst" instantiates undefined entity "asj_fft_sglstream_fft_110"
Error: Quartus II Analysis & Synthesis was unsuccessful. 1 error, 1 warning
        Error: Peak virtual memory: 246 megabytes
        Error: Processing ended: Mon Aug 05 14:42:34 2013
        Error: Elapsed time: 00:00:03
        Error: Total CPU time (on all processors): 00:00:01
Error: Quartus II Full Compilation was unsuccessful. 3 errors, 1 warning