Hello meantone,
We could have a look via a diagnostic file from you, to see what clues it might give and what we might be able to suggest, but we'd need you to upgrade to v4. (Hauptwerk version 3 was superseded by version 4 in 2011, and v3 is no longer supported in any way, I'm afraid.)
There are many, many major improvements in v4 above v3, so hopefully you would consider it worthwhile upgrading anyway:
https://www.hauptwerk.com/clientuploads/documentation/ReleaseNotices/Current/HauptwerkReleaseNotice.pdfIf you do decide to upgrade, and since I see you're in the U.K., you could order an upgrade either from our U.K. reseller (Douglas Henn-Macrae) here:
http://en.midi-organs.eu/index.php/shop/software/hauptwerk )
... or directly from us here:
http://store.hauptwerk-europe.com/Upgrades_c_30.htmlThanks in advance!
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.