I have a ASA5520 runing Device Manager Version 6.0(2)
When I launch ASDM and try to connect I get connection timed out.
The ASA is running transparent and I can ssh to the device.
http is enabled and the image is in the config.
The only thing I can see being the issue would be that I have the management interface disabled and accessing the device via the inside interface.
what else is there to look at?
If You can ssh to the device, I don't think the problem could come from a disabled management interface.
You have also specified the the IP address of the host and/or network authorized to access the HTTP server?
http ip mask inside
If this is not helping, try debug http, maybe this will give you some additional info about the nature of the problem.