Turning Display Alerts Off Causes Error

I've written a macro with the below code at the beginning:

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When it's run on the majority of computers that use it, it works perfectly, but for some reason when a few people run it, it errors out on the Display Alerts line. Has anybody else experienced this strange error? Is Display Alerts not valid in older versions of Excel?

This piece of code wasn't that important for this particular program, so I just removed it, and it works on all computers.

What's extremely strange about this is that the people who were having errors, have run this piece of code using dozens of other macros without any errors.

I'm pretty sure Displayalerts works for Excel 97 onward at least. What was the exact error they were getting?

They're not at the same location as me, and they didn't report the error name.

The person whose computer it's on is likely 2003. The really strange thing is the bit of code that caused this was copied and pasted from another macro that works fine on his computer. The file that didn't work on his computer also works fine on every computer I've tested at my location.

The file was stored on a website for him to access. If he clicked 'save' and downloaded it to his harddrive, then it worked fine. If he clicked 'open', then it would cause this error. Does Excel possibly block files opened from a temp location from changing certain application settings? I'm not sure how that would make sense, but it's the only thing I have to go on.