halogen lights wont work?

yes

The original transformer was supplying 80W of power and may very probably be rated 100W - Your extra bright 50W lamp will have pushed the transformer over its limit - it will have melted inside.

If you can find and remove the original transformer take it to a DIY store or a specialist lighting shop for a suitable replacement - will likely be much cheaper than a manufacturer supplied transformer and just as good.

Good luck...

Peccavi
December 2009