serious problem with export

After update to 6.oo, Cubase CANNOT export in NON real time…it exports the first minute, or some tracks.
Since update to 6.03, it exports only the first 5-6 seconds…in real time - no problem but I have some hevy projects that need NON real time…
I work with Cubase from 10 years and don’t tell me about muted tracks, multichanel export etc. .I have to re-open my projects with C5 and there is no problem, but its absolutely unacceptable… !!!