[amibroker] PlotShapes - help please

[c_r_south]

My PlotShapes function has decided to stop working on all calls. I use it in 
conjunction with 
alerts which are working fine. I've scaned the help files for the function and 
hide/show but 
can't find anything which I might have done to turn off the visibility of 
shapes. I'm at the 
'don't know where to look next' phase and would appreciate help.