There is a problem with the Powered Plug-Ins crashing Cubase 5.0r6 on launch or quit under certain conditions.  These conditions are three or more stereo audio tracks with powered Plug-ins on them in a session, and even then the crashes are intermittent.
The good news that we have found a workaround.  You need to open Cubase,
disable the audio, open your session, then re-enable the audio.  Before you quit, disable the audio again.
There are two ways to do this.  One is through the menus, and the other
is through the toolbar.  You can assign the Disable Audio function to a
button on the toolbar.

Workaround #1 is:
- Launch Cubase
- Go to Options / Audio Setup / Disable Audio
- Open your session.
- Go to Options / Audio Setup / Enable Audio
- Before you quit, go back to Options / Audio Setup / Disable Audio.

Workaround #2, with Cubase already open:
- Go to Edit / Preferences / Key Commands
- Click on the 'Options Menu' button
- Scroll down to 'Disable Audio'
- At the far right is the column 'ICON'.   Click there and choose an
icon.
- Click Apply and OK.
The Icon you choose will now be in the Toolbar (Windows / Show Toolbar).

When the async distortion problem occurs, you can disable and enable the
audio with this button and this can usually resync the UAD-1 card.
We of course understand that this is a workaround, and we are actively
developing a fix these issues.