VLAN missing — how to troubleshoot?

[mr530]

I have 5 vlans running on igb0 perfectly. Randomly 1 vlan stopped working today but the other 4 remain operational.  When rebooting, that VLAN isn't even attempted to be configured to the interface (while the other 4 are)

Any tips on how I begin to troubleshoot?

The missing VLAN prevents my ability to access the WEBUI so working directly on the appliance itself with a keyboard and monitor.

[cookiemonster]

please check for clues in dmesg and the output of ifconfig for starters.