I've just uploaded ElectrEm 0.6c, which is primarily intended to address
the following:

(a) sound emulation inaccuracies (especially audible in Arcadians)
(b) tape interrupt inaccuracy versus undocumented behaviour (caused no
display in the Hewson games Southern Belle & Northern Star —
infinite thanks to Tom Walker for figuring out the problem)
(c) possible Vista compatibility problems (though this isn't tested, as
I don't have it)
(d) very tangible OS X v10.2 and v10.3 incompatibility
(e) some other esoteric bugs that you probably didn't encounter

I'd intended to keep most of this until I'd added sufficiently many
other features to make this more of an interesting download, but (a) was
a bit of an embarassment and I thought developments on (b) justified an
"early" release.

As per usual, it's available from http://electrem.acornelectron.co.uk.