When this happens, I usually need to delete the .pc and .vr files from the virtual controller and the .pc on "file" menu from roboguide (same location as the .kl file)... then build again from the .kl, also sometimes I even needed to delete the .pc from the hdd directly or it doesn't want to build.
You must also do something similar when you modify the karel program if you have added or deleted variables, just delete the .pc and .vr files from the real controller before loading the new .pc since the associated .vr file sometimes is not overwritten after loading the new .pc.
Deleting the .vr ensures a new .vr will be generated again when you load the .pc.... I had weird behaviour and errors on a karel routine that made not sense... until I deleted the .vr and loaded the same exact .pc file that I loaded previously. If you want to delete the associated .vr file you first need to delete the .pc and then on "Type->All" will appear an .vr with the same name as the karel file you loaded.
Also... when building or loading a karel file ensure you have not called or selected that routine on the select/edit menu of the controller as it may fail to load after the build. Do an abort all and select another different program.
NP... this gave me an incredible headache like two years ago... do not trust the karel compiler.
I still continue to scratch my head every time a translation fails and it says that routine has not ennough of the required inputs (when some are in theory optional)... or that the data type is not compatible when the data is the same as the karel doc says....
Then a while ago I just discoverd that the console where errors are shown not only indicates the line where it fails, it shows also the problematic parammeter, you just need to search for a little arrow that points up on the next line just below the error text.
