I've identified a bug in this script; when a user includes an apostrophe or single quote in their "countdown finished" message, the countdown will not actively decrement. It looks like the single quote should be escaped. I'm looking at the script code now and will update when I have a fix.
Update:
In sktimer.js, I added the following as the first two lines in the CountBack function:
HTML Code:
FinishMessage = FinishMessage.replace ( "'", "& #39;" );
FinishMessage = FinishMessage.replace ( '"', '& #34;' );
(There are extra spaces in the above code between the "&" and the "#" because vB kept helpfully rendering the entities in the post. It should be "ampersand pound 39 semicolon" for single quote and "ampersand pound 34 semicolon" for colon, with no spaces.)
This just replaces single and double quotes with their HTML entity representations. I've attached the updated sktimer.js.
*** This solves the reported problem of only some user countdowns actively counting! ***