Hi, Andy -
I downloaded that file (specifically the version for OS 9) and it fully auto-decompressed without problem. This was using OS 9.1 and IE 5.1.7 and its built-in decompression capabilities.
I also tested the downloaded file which was decompressed from the source's .hqx file, one named "
NaViSet for Mac OS 9 V1.0.10.se" - the suffix should probably be .sea, which indicates it is a self-extracting file, one which does not need any assistance in order to decompress, but the name length exceeded OS 9's capability.
The file type indicates it was made by Stuffit Deluxe v. 7, but when I dropped it onto Stuffit Expander 5.5 it decompressed without a problem.
It also decompressed properly when I double-clicked that file, although it took a bit longer than using Stuffit Expander, and also required a response to a Navigation Services intercept (a request as to where to place the decompressed file).
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Based on that testing, it would appear there is nothing wrong with the download or the file itself. Rather, it may be a function of how your software is configured for decompression of files - what version(s) of Stuffit Expander you have available, what browser you are using, etc.
Try dropping the initial (uncompressed) file onto the icon for Stuffit Expander.