That could well be the solution; I was ignoring a warning about the fla containing a font that was not on my system - i didn't realise it would have such an impact.
Re the code pointer, many thanks - this isn't my code alas and I don't think I'd have done things this way. I'll have a look to see if there's a proper Timer class or something I can use to regularly run a now - startTime calc and display a to-the-seconds precision timer instead