A strange error has begin to appear when i use airodump-ng

root@bt:~# airodump-ng -c 7 --bssid xx:xx:xx:xx:xx:xx -w zzzz --ivs mon0
Invalid output format: IVS and PCAP format cannot be used together.
Why the ****k did it start happening.Searched the error string in google but no results!!!is this happening only to me???I'm updating daily to the nightly tarballs http://nightly.aircrack-ng.org/aircrack-ng/trunk/ by the way.