With an asa 5510 box we tried to upgrade the ASA version from 8.4 to 9.1. After starting the load from flash, it hung (see below). I ended up tftp booting an 8.4 version, and was able later to upgrade to asa version 9.0(3)6 without hang on boot.
I am not sure why the 9.1 load hung. It appears by my review of the documentation that this device is capable of running the 9.1 version. I'm not likely to try 9.1 until I understand the issue.
Loading disk0:/asa915-k8.bin... (HANG, local power cycle)
Booting system, please wait...
+ CISCO SYSTEMS
+ Embedded BIOS Version 1.0(11)4 03/21/08 17:09:54.41
+ Low Memory: 631 KB
+ High Memory: 1024 MB
+ PCI Device Table.
thanks for any ideas.