I have had good luck (depends on plastic-see below) with MEK
(Methyl-Ethyl-Ketone), works the same way as the dichloromethane, can
be acquired in most hardware shops. It doesn't work very well on some
of the "alloy" plastics (GE Cyclolloy? mix of polycarbonate and ABS.
Superglue doesn't even work here-the plastic disintegrates into a mealy
mush). Fortunately, that seems to be only used in newer Suns and PCs.
Drywaller's Fiberglass tape might be a good strong inorganic
reinforcer, or I sometimes use interfacing (a semi-fabric thing) when I
repair books- might work for computers too. In books, it seems to grab
the glue better than standard woven fabric.
-Scott Quinn