I concur with Pureh@te. If "iwconfig wlan0 mode monitor" works, what is the problem?
If you don't understand why we are asking this, I think you have a fundamental misunderstanding of what "airmon-ng start" is supposed to do. You might want to look into the basics of how wireless sniffing/cracking works so you understand why it is you are trying to run this command. (Here is a hint: check the man page for airmon-ng, then then check what the iwconfig command listed above does.....)
I though that
iwconfig wlan0 mode monitor
airmon-ng start wlan0
But should not airodump-ng work after you execute iwconfig wlan0 mode monitor?
it does not in my case! :\
is my case "airodump-ng" only work if "airmon-ng start wlan0" worked.
Your just not giving hardly any info to work with.
if you've put your card in monitor mode airodump-ng should be able to scan and sniff data regardless the way you've put your card in monitor mode. The only difference would be if you use airmon-ng and it establishes a new interface for monitoring (like mon0). Then you have to use that new interface with airodump.
But like Pureh@te said until you give some better info we're tapping in the dark.
The best would be to post the output of the commands that give you trouble.
Are you booting your vm-machine with your card attached to vmware? (not to host)