In Response To 'Re: Re: FindRoot not sovling a nonlinear system...'
I'm glad that my guess about what the problem was turned out to be correct and you were able to get your problem fixed as easily as you did.
As far as I know, I don't think anyone has figured out the TextCell[""] are getting in there. This is probably partly because they are almost invisible and people just don't notice them at the moment they are introduced.
If I had to guess, I would think they might result from very subtle flaw in the front end coupled with some subtle odd way of using the front end.
If I thought there was any chance I would be able to generate one of these I would arm the system with an alarm to let me know the instant one of those showed up, but it seems that the way that I do things just doesn't seem to generate these.
I remember someone 5-10 years ago that I was trying to help when it turned out that he had somehow ended up with something like x+" "5 in the middle of a calculation, but those quotes were invisible in the notebook. We never did figure out how that got in there, but I think the conclusion was that this tended to happen with individuals exchanging notebooks.
Perhaps in a future version there could be a warning message introduced that would point these out and the problem could be tracked down and overcome.