The balance sheets of Europe's banks hold big opportunities for private equity firms seeking pre-crisis real-estate loans at a discount, but the complex portfolios also come with big risks — and major headaches for interested buyers. As a result, the deluge of distressed real-estate portfolio sales by European banks that was expected after Lloyds Banking Group and Royal Bank of Scotland Group's year-end deals will feel more like a trickle in early 2012, experts say.

Banks' sovereign debt exposure, the complexity of transactions and the gulf in price expectations between private-equity firms seeking deals and banks hoping to mitigate their losses, will continue to weigh on the pipeline of large transactions.