Another idea is to 'play' it back directly from the computer to the Polaris (i.e., Audio from PC directly in to 'cassette in' on Polaris) vs. going to the intermediate step of putting it on cassette. Depending on your setup this may give you a bit more control over the levels going into the Polaris, and give you more luck about having it load.
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Re: [chromapolaris] continuing cassette loading issues:
2007-10-19 by David Clarke