IMac won't sleep external monitor

I have an intel imac and I've been using it about a month. Today I noticed that the second screen (Hp L2335) is not going to sleep when the imac is. The monitor is hooked up via the mini DVI adaptor cable I purchased.
The monitor seems to be able to do sleep mode in its other functions but when I try to get it to go to sleep with the imac, the screen just stays frozen as if it captured the last frame. When I wake the imac, it updates and is active. I know this because I'm using it as the primary monitor and I can see the digital clock in the upper right.
anybody else ever had the same problem?

this problem seemed to magically fix itself after about half a week.... I'm not sure what was going on.

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If you have Disk Warrior, then use it to check the state of the HD directory. Directory errors can trigger oddities in the system. If you don't have it, open Disk Utility in your Utilities folder and "verify disk", seeing if any errors appear. DU is nowhere as advanced as DW; hence, errors may be present beyond the capacity of DU to detect or repair them.
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Tristan Currier noticed this; "I have a Canon printer(shared) and my imac would not sleep. I opened up printer/fax in system prefs and noticed it said the printer was in use when it was off. Opened up the printer queue and noticed about 7 pending documents. Deleted them all and now it sleeps.
Check the printer queue!"
Good Luck!  DALE

IMac won't sleep external monitor

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