[R-SIG-Mac] Plot title style change in Leopard (or, "Where art thou, bold?")

[thatsanicehatyouhave at mac.com]

Hi List,

Since upgrading to Leopard, the font (or just style?) of my plot  
titles has changed. They used to be bold but are no longer. I tried to  
force it using:

plot(1,1, main=expression(bold("title")))

... but there's no difference to

plot(1,1, main="title")

Am I missing a font or has something else changed? I need the old look  
since I'm in the middle of a long document and I'd like consistency  
with the plots I've made up to now.

Cheers,

Demitri