I have this bug (bad vlan interface name) on several ubuntu dapper :

# vconfig add eth0 100
Added VLAN with VID == 100 to IF -:eth0:-

# cat /proc/net/vlan/config
VLAN Dev name | VLAN ID
Name-Type: VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD
eth0.100_ifrena| 100 | eth0

packages :
- vlan 1.9-1
- ifrename (same bug when this package is installed or not)

Somebody has any idea ? Because it's not easy to configurate vlan interface when the interface name change ...