Ahh yes ... the dreaded 80000003 guru.
I have never used Amplifier or Melody1200Pro, so I can't give you a definite answer.
80000003 is the most common guru I get on my Amiga 2000HD, which is equipped with a 68000 CPU.
Through trial and error I found that this failure code seems to be a catch all for many problems I have encountered over the years.
Sometimes, it means that there is 68020 (or later) code in the program or an associated library. The 68000 CPU usually takes a visit to the guru when it encounters this code.
Certain programs cause problems for certain other programs. Certain programs will also interact with each other, causing system stability problems.
Sometimes, it means that the program can not find certain required files or libraries, they may simply be in a different directory or on a different drive than the program expects to find them.
Sometimes, a new program requires a newer version of a library that already exists on the system. If you don't update the library, the new program may crash. If you do update the library, other older programs may be crash.
Good luck .... I hope you get a more definite answer.
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redfox