VLAN Tagging it works, now it doesn't?

My Setup is a 2830n -- M0n0wall firewall -- dellswitch --ap800 x3 (FW1.0.3). 12VLAN'S. The aim is to get 12 wireless networks each tagged to the 12 VLANS. simple?!?

I have setup the m0n0nwall up with 12 vlans and everything is working OK network running like a dream. anyway I set up one of the AP800's up patched via Vlan100 id, it was initially a bit of a nightmare to configure but managed to get it working with 2 SSID's running both from LANA's. all good so far, added different VLAN ID's to the SSID's and it worked great it was supplying the correct DHCP addresses when flicking between the 2 Wireless networks. (life was good). anyway back a week later and it's stopped working? no idea why (life not so good) I added a couple of rules on M0n0wall to allow HTTPs and FTP through but this should not of caused the issue, I deleted them anyway and still no joy.

I have pretty much gone through it all trying to work out what's going on and I am stumped...

I have upgraded the firmware from 1.0.2 to 1.0.3, set to default setting, turned off and on and off LANB, changed security. I have even rebuilt the M0n0wall. VLAN tagging does not work. if I set the VID to 0 it works and supplies a VLAN100 IP address as soon as add 500 into the VID field I connect to the wireless SSID but it self assigns an IP (194 something or another). No internet...

What a fu***ng nightmare, pardon my french.

Anyone got any suggestions?

Merci