Invest downpayment for a new house?

[AKnogoood]

I’m 28 years old and I live in Canada. I’m planning to buy a $200K house in about 8 to 20 months (in January 2008 or January 2009). I currently have $90K in a cash optimizer account at ETrade.ca (4.15% interest) that I will use as a downpayment. I don’t know much about stocks and that’s why I decided to put my money there.

I recently read the sticky “Investing 101 for Trout” and I was wondering if it would be wise to invest this amount in an Index Fund EFT (some posters suggested Vanguard EFT). I could tolerate a maximum loss of $20K per year on that investment.

So do you guys think it would be a good idea? Or do you have any other suggestions as to what I should do with that $90K? Thanks.