Decaying foam on PCBs

[Jules Richardson]

I picked up a couple of HP 5036A logic trainers today, both of which have 
had goopy decaying foam come into contact on their PCBs. What's effective 
at removing it? I've only ever had problems with it in locations where I 
can use things such as citrus-based cleaners, but I'm a bit wary of using 
those around a PCB. Is regular Dawn/water likely to work?

thanks!

Jules