i think the best rule to apply is only invest an amount you can happily afford to loose without having any impact at all on your life and that you can keep tied up long term,
If Northern Rock were to be bought (which is looking more likely) then the share price is very likely to rise. Therefore it could prove to be a good investment. However it could prove to be a risky one.
I have bought some......!!!! Look at it as being the January sales as far as buying opportunities are concerned!!