I have recently completed prgmONEVAR, a program designed to solve one variable algebraic equations. However, on the last line of code, an ERR:SYNTAX occurs, and Goto, strangely, goes to "prgmONEVAR", with the "E" highlighted. Why is this error occurring, and how can I resolve it?

It appears that this was solved.

It appears that this issue has already been solved over SAX. The problem occured on the last line of the code which included an expr(). It tried to evaluate a string that had invalid syntax (i.e. "1+-"). The TI-Basic editor redirects to the homescreen with the program name when you try to Goto the error involving expr().

How come "Disp Str9Pause Str9":expr(sub(Ans,1,2)) doesn't work?

As solved on SAX, expr( can not be used to run "Disp Str9". This is due to a limitation of expr( in which the string that is being evaluated as the expression must return some sort of answer.
Running the above code in a program will result in a syntax error. However, when you try to goto the error, it will just bring you to the homescreen.
Running the same code on the homescreen will result in an invalid error.
More information can be found here.