Imac won't restart from sleep mode

Have just joined as new member. Have a problem with my computer re-starting after going into sleep mode. Computer does not respond to mouse or keyboard. Only action is to restart computer and consequently lose unsaved work.
Have printed off the report but not sure if the info is useful. Help would be appreciated

Please provide us with a screenshot (Cmd-Shift-4) of your Energy Saver settings, both the Sleep and the Options (if they still exist in Leopard). Secondly, is your computer on a UPS or Surge Protector? There may be power supply problems, and your Mac is reacting to a power flutter as the monitor lights up again.

You say you've printed a report. Is that from the Console Log? You can attach the report to your reply post. Others who know more than I about how to analyse the report can then respond.

I'm sure you realise this, but it pays to save your work every time you leave your computer for any length of time

Thanks for reply. Problem didn't happen yesterday but did again today. Below is the report the computer generates after rebooting. To answer your points. Computer is on a surge protector but it doesn't feel like this is the problem. Essentially I have to hold my finger on the power button until I hear the machine shut down. I then have to push the power button again to restart and the message below is generated. I'll send a separate message for the power settings. Appreciate your help.
Wed Aug 20 09:03:31 2008
panic(cpu 0 caller 0x001431A9): "zalloc: \"kalloc.8192\" (43 elements) retry fail 3"@/SourceCache/xnu/xnu-1228.5.20/osfmk/kern/zalloc.c:770
Backtrace, Format - Frame : Return Address (4 potential args on stack)
0x34877c88 : 0x12b0fa (0x4592a4 0x34877cbc 0x133243 0x0)
0x34877cd8 : 0x1431a9 (0x45aef0 0x459b38 0x2b 0x3)
0x34877d38 : 0x12fa53 (0x1c842d8 0x1 0x46fd5c0 0x15)
0x34877d68 : 0x12fa72 (0x1690 0x1 0x15 0x0)
0x34877d88 : 0x11d99f (0x1690 0x7fffffff 0x0 0x1)
0x34877db8 : 0x12d0f6 (0x10f0 0x4d81168 0x34877df8 0x11ee14)
0x34877df8 : 0x126257 (0x23754c00 0x3fbe844 0x4d81168 0x0)
0x34877f08 : 0x1973dd (0x34877f44 0x0 0x0 0x0)
0x34877fc8 : 0x19f3b3 (0x4b675e0 0x1 0x1a20b5 0x4df8208)
No mapping exists for frame pointer
Backtrace terminated-invalid frame pointer 0xb007f3f8

BSD process name corresponding to current thread: hpdot4d

Mac OS version:
9E17

Kernel version:
Darwin Kernel Version 9.4.0: Mon Jun 9 19:30:53 PDT 2008; root:xnu-1228.5.20~1/RELEASE_I386
System model name: iMac7,1 (Mac-F42386C8)

 Hi Again. The Power Settings that I have are as follows:-
Sleep.
Computer goes to sleep when it is inactive for 15mins.
Display goes to sleep when the computer is inactive for 15mins.
Box is ticked to put the hard disk to sleep when possible.
Options
Box is ticked for Wake for Ethernet network administrator access
Box is ticked for allow power button to sleep computer
Box is blank for restart automatically after a power failure.

Sorry there are no screen shots but can't get that to work. Probably my limited ability or that I have an Apple Wireless Keyboard. Probably the former.
Once again, thanks for your help

stevel2 said:

The Power Settings that I have are as follows:-
<snip>
Options
Box is ticked for Wake for Ethernet network administrator access
Box is ticked for allow power button to sleep computer
Box is blank for restart automatically after a power failure.

Sorry there are no screen shots but can't get that to work. Probably my limited ability or that I have an Apple Wireless Keyboard. Probably the former.
Once again, thanks for your help

Click to expand...

Okay, for a start, uncheck that "put hard disk to sleep when possible". I don't guarantee that will cure the problem, but it's one place to start. The other settings are pretty much normal.

Re your screenshot or image grab:
1.hold down the Cmd & Shift buttons and then hit the 4 button with your other hand.
2. Crosshairs will show, which you can move with the mouse, and then
3. Click and hold its L-button and drag to select the particular area you want the Mac to photograph, then
4. Release the L-button.
The image will be saved automatically to your desktop as Picture n (a number).
Failing that, Cmd-Shift-3 will take a complete screenshot.