Dear Sean,

Thanks a million, I could have been staring at it for two lifetimes... I guess you're right, subscripts can be a pain after all; still thinking in terms of chemistry I guess...

Thanks again for taking the time, and for the advice!

1. Take your first cell, where you defined "odes" and highlight it.
2. In the toolbar, navigate to "Cell" > "Convert To", and then click "Input Form"

Your code will look different. You should think of this as how your code "actually" looks.

Now, inside of your code you will see "TextCell[""]". This means you have an invisible TextCell accidentally inserted into your code. Get rid of it and then try rerunning your code. Does this help?