Cannot Start VM when CD/DVD Passthrough enabled

[wahisfun]

Using VB 2.0.4. XP host ubuntu 8.0.4 guest. The guest machine will start perfectly and can read the CD/DVD drive when the CD/DVD passthrough is NOT enabled. But, the guest system does not see the CD/DVD Writer for burning a cd. I read that the passthrough feature is supposed to allow this but when I enable passthrough, I cannot start the guest OS. I get a box status code 38 (VERR_ACCESS_DENIED).

Any help?

Thx