WordPress hangs with Dashboard plugin enabled

WordPress hangs when with WPMU DEV DASHBOARD (ver 4.0.4 ) plugin is enabled

Error log:
[25-Jan-2016 12:30:27 UTC] [WPMU DEV Dashboard Info] Project Auto-Upgrade result for 119: Failed...
[25-Jan-2016 12:30:28 UTC] [WPMUDEV Dashboard Error] HTTP Error: 599 ""
[25-Jan-2016 12:30:28 UTC] WPMU DEV error: Upgrade failed - U001. Enabling Maintenance mode…
The plugin is at the latest version.
Disabling Maintenance mode…

Please resolve.

Regards
AJ