Hi Paul,
This happens all the time so it shouldn't be a problem :) I am guessing you received this AP - AIR-LAP1131AG-x-K9 LWAPP. When you really wanted this AP - AIR-AP1131G-x-K9 Cisco IOS Software. Have a look at the comparison;
http://www.cisco.com/en/US/products/ps6087/products_data_sheet0900aecd801b901c.html
That being said you should be good to go with 12.3(11)JA1;
Release Notes for Cisco Aironet Access Points for Cisco IOS Release 12.3(11)JA1
http://www.cisco.com/en/US/docs/wireless/access_point/ios/release/notes/b11jar1n.html
Cisco IOS Release 12.3(11)JA1 supports autonomous 32 Mb platforms. 16 Mb platforms and platforms supported by Cisco IOS Release 12.3(8)JA and earlier (350, 1100, 1130, 1200, and 1230 series access points and 1300 series access point/bridge) are supported by Cisco IOS Release 12.3(8)JEA1.
****Don't install a "JX" (This is a Cisco Lightweight Access Point Protocol (LWAPP) upgrade and recovery support software image);
These release notes describe features, enhancements, and caveats for Cisco IOS Release 12.3(11)JX1.
***Note: This release must only be loaded onto access points at the factory or by using the Autonomous to Lightweight Mode upgrade tool. Your access point might become inoperable if you install this software without using the upgrade tool.
http://www.cisco.com/en/US/docs/wireless/access_point/ios/release/notes/b311jx1.html
Reverting the Access Point Back to Autonomous Mode
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html#wp161272
You can convert an access point from lightweight mode back to autonomous mode by loading a Cisco IOS Release that supports autonomous mode (Cisco IOS release 12.3(7)JA or earlier). If the access point is associated to a controller, you can use the controller to load the Cisco IOS release. If the access point is not associated to a controller, you can load the Cisco IOS release using TFTP.
Using a TFTP Server to Return to a Previous Release
Follow these steps to revert from LWAPP mode to autonomous mode by loading a Cisco IOS release using a TFTP server:
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Step 1 The static IP address of the PC on which your TFTP server software runs should be between 10.0.0.2 and 10.0.0.30.
Step 2 Make sure that the PC contains the access point image file (such as c1200-k9w7-tar.122-15.JA.tar for a 1200 series access point) in the TFTP server folder and that the TFTP server is activated.
Step 3 Rename the access point image file in the TFTP server folder to c1200-k9w7-tar.default for a 1200 series access point, c1130-k9w7-tar.default for an 1130 series access point, and c1240-k9w7-tar.default for a 1240 series access point.
Step 4 Connect the PC to the access point using a Category 5 (CAT5) Ethernet cable.
Step 5 Disconnect power from the access point.
Step 6 Press and hold MODE while you reconnect power to the access point.
Step 7 Hold the MODE button until the status LED turns red (approximately 20 to 30 seconds) and then release.
Step 8 Wait until the access point reboots, as indicated by all LEDs turning green followed by the Status LED blinking green.
Step 9 After the access point reboots, reconfigure it using the GUI or the CLI.
From this doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html#wp161272
Hope this helps!
Rob
