I received the same error message as well while still using 10.5.6.
I downloaded this updater on or about May 6th:
"ParallelsDesktop-parallels-en_US-4.0.3844.408728"
I used the installer to "remove" the older version and then installed the new version. When I tried to use my VMs, I received the same error message to which others are referring:
"one or more kernel components..."
So, as far as I can tell this is not a 10.5.6 problem. It's an issue with the Parallels update 3844.
OK, I am convinced that I have a solution.
Based on what I have seen, 10.5.7 is NOT the problem. Its the v3844 updater of Parallels. It does not remove some of the extensions from an earlier version. Parallels see these and creates the warning.
There may be an exytra step in here, but I know this solved the problem for me:
1) Use the "Uninstall Parallels Desktop" utility in the v3810 dmg package to remove Parallels. When you run the Utility, Select "Parallels Desktop" and "Application Settings" for removal.
2) Restart
3) Run the installer on the v3844 dmg image.
4) Navigate to the following folder
/System/Library/Extensions
And move the following items into the Trash (you will need to enter an Admin PWD).
dprl_hid_hook.kext
prl_hypervisor.kext
prl_netbridge.kext
prl_usb_connect.kext
prl_vnic.kext
5) Restart
6) Parallels should now load and not give you the warning message.
Again, there may be an extra step in here or some overkill. Maybe you do not need to select "Application Settings" during the uninstall. You also may not really need to use the older v3810 dmg image. But know that the above worked - at least for me.