I think you might be running into this issue because the 1242 AP supports the Intelligent Power Management feature (which I didn't even know existed until recently). Have a look at the following.
Power Issue with the AP
When an AP uses a power injector as the power source, in some cases, the AP displays this error message:
CDP_PD-2-POWER_LOW: All radios disabled - LOW_POWER_CLASSIC inline
This message indicates that the AP is in low-power mode with all radios disabled and detects a Cisco switch that is unable to supply sufficient power to the AP. Even though the power injector, which can provide sufficient power, is connected with the AP, the AP still displays a LOW POWER error message and disables the radios. Therefore, the AP remains in low-power mode.
One possible reason for this issue might be that the AP supports the Intelligent Power Management feature. The Intelligent Power Management feature uses Cisco Discovery Protocol (CDP) to allow powered devices, such as an AP, to negotiate with a Cisco switch for sufficient power. The AP supports the Intelligent Power Management feature. As a result of the power negotiations, the AP either enters full-power mode or remains in low-power mode with the radios disabled.
In this case, the AP might be connected to a switch which cannot provide the necessary power to the AP. Therefore, even though the power injector is connected to the AP that uses this Intelligent Power management feature, it gives priority to the CDP information to identify whether or not the switch can provide the power. Once the AP knows, via CDP message, that the switch does not provide sufficient power, it disables the radios and remains in low-power mode.
The workaround to this issue is to tell the AP to ignore the CDP information for power. You can perform this by telnetting into the APs. Issue these commands to enable the APs to use the power injector:
power inline negotiation prestandard source
power inline negotiation injector H.H.H
The power inline negotiation command configures the Cisco Aironet 1130AG or 1240AG Series AP to operate with a later version of switch software that does not support Cisco Intelligent Power Management power negotiations.
The prestandard source portion of the command specifies that the Cisco switch runs a later version of software that does not support Intelligent Power Management negotiations, but is able to supply sufficient power to the AP.
The injector H.H.H portion of the command specifies that a power injector supplies power to the AP, and that the AP connects to a new switch port with the indicated MAC address (H.H.H). Enter the MAC address (in xxxx.xxxx.xxxx hexadecimal format) of the new switch port where the power injector is connected.
Note: This command should only be used when you move an AP and power injector to a different switch port.
Nice job in helping to troubleshoot this issue. It sounds like you are pointing Paul in the right direction. The only other power related sympton I have seen is the continual rebooting of APs when the power capabilities of the switch (Pre-standard) don't match the settings on the AP. Similar to what you have pointed out.
Even if this isn't the answer for this question you have provided everyone who reads your answer with a fine tutorial on power issues related to access points. I rate this a "5" and will continue to look for your answers in the forum.
Thanks so much for taking the time to read and rate peoples posts here! I am flattered that you have found something good in the info I provided :) The nice comments from you mean more to me than you will ever know. I am also rating you 5 points for the most valuable addition you are to this community!