Sorry, the appearence of your reply inexplicably failed to set off my pager
We get to look at questions when we can, and answer those we can/want. There is no point in prompting for replies, it is more likely to have the reverse effect.
I am genuinely sorry for initially dismissing your problem as the misplaced continuation indicator. I didn't know that the Code tags would do that.
When you get an error message you are unfamiliar with and cannot understand in its own right, then you have to look at the full description of that message in the supporting documentation for the product. This is no matter what particular software you are using.
Like Dick, I have not used this Assembler product, so echo his suggestion. I tried a quick google, but no immediate help to me. It might be worth you trying, and especially when you know a bit more about the error if it persists.
Maybe at the same time, "isolate" the first OPEN in a seperate program (copy, then remove all the code which is not needed for the OPEN and assembly to work).
If still stuck, let us know what you have tried, and we can think again. Maybe with the Code tag problem with the Xs, delete blanks in front so that they appear on the same line at the extreme right of the Code box, and mention that.
Let us know, whether you resolve it or your problem continues.