Hi,
Under the "AsyncOS Reversion" it states the following:
"AsyncOS for Web 7.5 supports the ability to revert the AsyncOS for Web operating
system to a previous qualified build for emergency uses. However, you cannot
revert to a version of AsyncOS for Web earlier than version 7.5."
I hope this helps,
Luis Silva
"If you need PDI (Planning, Design, Implement) assistance feel free to reach"
http://www.cisco.com/web/partners/tools/pdihd.html
Luis Silva