How can I fix the windscreen wipers on my Vauxhall Zafira?

I put my wipers on yesterday but they had frozen to the windscreen. I defrosted the windscreen - the wipers now move but keep crashing into one another and getting stuck, resulting in the lower blade tearing. Any ideas how to sort this out as I don't want to put new blades on if it's going to tear again
btw it's an old style 1999 Zafira

Tom
March 2007