NiceBigMan,

вот по теме, такой же вопрос обсуждается
https://forums.oracle.com/forums/thread.jspa?threadID=846758&start=0&tstart=0

может можно как то попробовать File->Convert->binary to text и обратно, и смотреть на что ругается...
а вообще там архитектура принципиально другая

основные выдержки:
Grant Ronald: there is no supported way of doing this....sorry

Well you could open the Form in 10g and then cut and past the code and triggers into the 6i Form which is open in 6i. But you would have to create the blocks and canvases yourself and the cut and pasted code might not always work if it is using 10g specific features.

Please please warn your customer about the dangers of going back to an almost 10 year old desupported product version!!!!