Let me guess... you have an ATX psu, and NOT an origional A1200 psu? Right?
Whoever sloppy dude who connected that ide cable, may also have done a poor job somewhere else in the machine. Check all the other cables and make sure they are connected properly. And I mean PROPERLY! The powercable connected to the internal floppy may easy get connected wrong, and shortcircuit your psu.
An ATX psu will in most cases shut down after a while, everything between 2 seconds and a few minutes. But in most cases after a while the psu will DIE and take you hd down along with it.
Happend to me... :-x Doh! Tricky little problem...
The red cable on the ide shold not matter in you case...
1, Check all yor cables.
2, Try testing your machine with a new psu.
3, If a new psu down't solve your problem, then you still have a shortcircuit... :-o
