Originally Posted by DiapDealer
I suspect you're trying to force all 52 characters into the Palm Database Name. Don't do that. Palm Db names have to be 32 bytes or less (it doesn't matter if your title is longer than that). Put the full title in an EXTH record (type 503). Devices/apps will use that for the metadata. They will only fall back on the Palm database name if there is no full title elsewhere in the mobi.
I know about that limitation and I think Calibre may write a larger title, but there is no way to be sure since there is no way to access the metadata... I get the error I told you about even if I don't try to modify the metadata, only read it. Not to mention I also get that error if I try to modify it. So as far as mobi2mobi is concerned the file is ruined.
Again, the weird thing it doesn't happen for all large title files... I have reconverted another large title book in Calibre and it works just great in mobi2mobi.