I seem to have the same problem (i think), since an update a few days ago i can only send packets when using a tagged cable run. If i use an untagged run it works fine (DHCP offer, ping, ect). I have tried another MAC on the vlan ifcfg but the vlan wouldn't even come up with that config (as suggested earlier).
I ran a wireshark capture on my nic and my mac is not in the destination of any of the packets. I cannot even ping anyone in my own subnet (on the same vlan) so no routing is involved.
I ran wireshark on another machine (same subnet) and ping'd that machine, it received all and replied to all. None received.
Using a HP Procurve 2910.
uname -r: 2.6.40-4.fc15.1686
Samsung Netbook N150Plus
I am sure there is more info that you need
p.s. all my vlan ifcfg files are set to ONBOOT=no as they are only used when in work. The usual p9p1 if is dhcp onboot for normal dhcp networks, i.e. home.