Yes, I just did the same thing. You will need to download the upgrade file with the pkg extension (not the image file which I kept trying to do). The file is: IPS-K9-6.1-1-E2.pkg under the security software, Software Upgrades.

Link:

http://www.cisco.com/cgi-bin/tablebuild.pl/ips6

Once you have that file, either put it on an FTP server, or put the file on the local client that you are using to connect to the IPS with IDM. You will need to go to Update Sensor within the IDM and either choose FTP or the local update path and point to the file. The sensor will reload when it is done, but will not reboot you ASA. It will take about 5 minutes, and then you should be able to reconnect to your sensor with the IDM.

Here is a helpful link on upgrading:

http://www.cisco.com/en/US/docs/security/ips/6.1/configuration/guide/cli/cli_system_images.html#wp1231089

Here's a link on making a backup of the config:

http://www.cisco.com/en/US/docs/security/ips/6.1/configuration/guide/cli/cli_configuration_files.html#wp1033167

Hope this helps!

Jason