It is a bug in the editor for all 6.0x versions.
It gets better in 6.02 but once such an insane error appears you should immediately try to eliminate it. Eliminating can be done in a binary search.
1) Save your vi under a new name say temperror.vi.
2) edit this temperror.vi by removing half of the vi.
3) save it and watch for the insane error.
4) if it still exists remove another half otherwise start anew with the original copy and repeat those steps until you find the insane object or wire.
If you don't remove this error as soon as possible it will make your editor more unstabe and at the end it will crash !
greetings from the Netherlands