Hi,
normally i'm using EAC to produce MPCs with version 1.1 of mppenc.exe. I've configured EAC to tag all files with ID3V1 and V2 (i hoped that there'll be a decoder which supports that). But now i've heard of Replaygain and how it works and so it tried to use it with my files. But when calling 'replaygain --auto *.mpc' on the commandline it says that it can't decode those files. In this forum i've found a topic where it was said that the id3v2 tag should be removed. Thats why I called 'tag --force ape2 --removeid3v2'. It told me that it has removed the tag and everything is OK. But ReplayGain gave me an error again. So I used 'tag --remove' and hoped that it would solve all problems. But it didn't. I had to remove all the tags within WinAMP for each song. After that everything worked fine.
But now I habe around 900 MPCs so it is too much work to remove the tags on that way. My Question: What can I do?

Only thing preventing replaygain from working is ID3v2 tag. You removed it succesfully with Tag so everything should have worked after that. Winamp tagger can't remove ID3v2 tags and no other tag has any effect on replaygaining success.
I'd have to guess that replaygain didn't manage to find mppdec.exe initially, but I have no idea why it worked later. Download this mppdec+replaygain package, install the files under path and try again. Copy/paste here all error messages from console if things aren't working correctly.

I beg to differ - Radioactiveman's experience is not unique. In a similar thread a few days ago, I mentioned to you that I was having problems with replaygain crashing on certain files with (supposedly) only APE2 tags - removing them, RGing, and re-tagging worked. Since then, I've found more cases - no more crashes, but now RG is producing 0's for both gain adjustments and 1 for peak values. Removing all tags again fixed the problem. All of these files are MPCs which were tagged with id3 + id3v2, then "tag --remove --force ape2," with tag reporting successful removal, with resulting files showing as having only APE2, yet still fail to replayagin until a "tag --remove" is run on them. So either one of two things is happening - either tag is not fully removing id3v2 tags... leaving some 'residue' behind that confuses replaygain, or replaygain has problems with APE2 tags... problems which only manifest in a small minority of cases.

Oddly, in all the cases I've discovered of this happening, all the albums from a given artist are affected by it... meaning with the original crash problem, whenever I came to an album which would crash replaygain unless tags were first stripped, I would strip the tags, restart my replaygain 'sweep', only to have it crash the next time through on a different album by the same artist (and continue for as many albums by that artist were in the batch). Now, with the newer problem, when I'm going through my collection and see a given album which has 0 gain adjustments, I look and see that everything else by the same artist does as well. I have no idea why this would be.

If you want, when i get home I can paste a transcript of the RG output - but it doesn't give any kind of error, it just detects zeros for everything and acts as if that is correct.

These problems sound very strange. I need to know what version of mppdec.exe you have and what replaygain.exe you use. Replaygain version number doesn't say much, it hasn't changed for ages, but I need to know where it was downloaded from.
Also if you manage to make replaygain fail on one particular file, it would help if I got that file for testing.

I'm pretty sure I'm using the latest versions of everything, but when I get home I will check and post version numbers, output transcript, and an offending file - how should I go about getting the file to you? Is email ok?

Address cse at sci dot fi shouldn't have size limits, so you can use that.