One cause could be related to firmware. Are you using the latest one (Version 1.08)?
Also the enabling of GigaRec is valid only for the INSERTED disc. As soon as you change the disc, the setting is reverted to normal. So you have to insert the disc first, then enable GR, then burn.
Other limits apply:
- During recording, Buffer under run proof will not work.
- Only DAO (disc at once) mode is supported.
- Only CD-R media can be used.