[DiapDealer]

It's not the mobi format in general that's the problem. It's the extra bits that dictionaries use. There's always been issues with infections and such. I'm not the expert there, so I can't really say what the trouble is with mobi-dictionaries.

You might try calibre. I don't know if it will do any better on dictionaries.

But more than likely, anything that claims to convert/unpack mobi files/dictionaries is probably based on calibre or KindleUnpack code (and thus the same limitations). And a lot of the mobi stuff in KindleUnpack was ported from the older Perl-based Mobiperl project. Somebody blasts though every now and again with high hopes of creating a C/C++ or C# version, but I'm not sure if anyone has a fully-functional alternative yet.