RSL5000 Source Protection

Can anyone explain how "Source Protection" works in RSLogix5000? I have a Compactlogix controller that I have previously been able to edit the program, but now several (most) of the routines that I have edited before are now unable to be edited. The PLC and the PC that I use to edit it (which is also the HMI)are not hooked up to any network beyond the local machine and no one with any PLC knowledge has been near the PC besides myself. The routines that I cannot edit say "Source Protected: Source Key Not Found". This is for a boiler we have, and the manufacturer has supplied a backup PC as well that does the same thing. Since it is Friday I have not been able to call them to find out if they may know what happened, and I would like to learn about it I thought I would post this for you guys to educate me.

the type of protection you are talking about revolves around a small file (usually named "sk.dat") which needs to be located where the RSLogix5000 software can find it (usually in the same directory as the ACD project file) ...

anyway - some of your code may be specified as "protected" - while other sections may not - but for those sections that ARE protected, then "no key - no entry" ...

I have heard horror stories of the IT department "cleaning up" a computer's hard drive - and removing the "unused" and "unknown" sk.dat file ...

for more detail, here's a link to some screen shots on a "work still in progress" webpage that might be helpful ...

http://www.ronbeaufort.com/CLX_Source_Protection.htm

for even more detail, notice that there is a link to Allen-Bradley's official documentation on this subject near the very bottom of that page ...

Thanks Ron, that info will be a lot of help. If I cannot find the SK.dat file I may have to contact the boiler manufacturer on Monday to help me as they should know the password if one exists somewhere. I will post back to let you know what I find.