every now and then this appears and hangs around untill I press the ok button 3-4 times.
The error happens when I run .exe's and I've no idea what its trying to tell me.

anyone got some ideas?

it has to do with kernel32.dll, but u figured that one out 2...
redownload kernel32.dll
http://www.dll-files.com/dllindex/dll-files.shtml?kernel32

I assume zlclient.exe (a part of ZoneAlarm) isn't doing its job fully at the moment. Unfortunately with no additional info the issue could be traced to several options: ZoneAlarm malfunction, malware, missing or wrong files, even a hard disk problem.
What would I do?
1) Check the system thoroughly for malware and have a quick look at file system and hard disk SMART parameters.
2) Uninstall/Reinstall Zone Alarm, or upgrade if possible.
I would also take a look at the System Service Descriptor Table to see if ZoneAlarm traps some calls to the kernel, and disable ZoneAlarm to see if the error appears again. But I would do this after a thorough analysis of what's running on the computer to be sure not to cripple it in a stupid way.
One thing I wouldn't do, FOR SURE, is blindly substituting kernel32.dll without having a clue about it. It may be a difficult task substituting it on the run but hey, I've seen many stupid and difficult "repair" actions succeed in my career. And at least twice as many fail.

Do _not_ replace kernel32.dll.

0) Deep, safe-mode virus, rootkit and spyware scans
1) Uninstall all zone labs products
2) Re-download, reinstall
If the problem persists,
3) Open command prompt and run the command sfc /scannow, it will check all your system files for authenticity, and will ask you before replacing any existing ones with original versions
4) Repair install, anything but put random system files on your pc.