Descriptive Problem Summary:
In version 500 and beyond the missile proc does not work. There is no visual effect at all.
I've tried it in projects compiled with version 500, and projects made in older versions but run in 500 and the problem is present in both.

Numbered Steps to Reproduce Problem:
Use the missile proc.

Expected Results:
You see an image move from one location to the other.

Actual Results:
You don't see anything.

Does the problem occur:
Every time? Or how often? Everytime.
In other games? Yes.
In other user accounts? Yes.
On other computers? Cannot test.

When does the problem NOT occur?
I've been unable to get missiles to appear.

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)

Before upgrading to 500, I was using 499.1198 and it was working fine.

Workarounds:

Use an older version.