sniffing 802.1q

Hello all,

Could someone give me an explanation about this:

I’ve got 2 PCs, PC A & PC B.
I connect them to a 10Mb hub.
On PC A, I generate 802.1q traffic with my sniffer pro (64 bytes packets) and I sniff this traffic. I can see the 802.1q tag in the capture.
On PC B, I sniff the traffic on the hub. And here I sniff the packets sended by PC A, but without the 802.1q tag. The packets are only 60 bytes long.

The hub is transparent, so it happens something on my NIC.
When I generate traffic on PC B, and sniff on PC A, I get the same problem.

thanks fo your help

JP