Year-over-year home prices up 3.8% in April

But that was affected by the tax credit that ended on April 30th:

Home prices rose 0.8% in April compared with March and were up 3.8% from a year ago, according to the S&P/Case-Shiller Home Price Index of 20 major housing markets.

That good news is tempered by a couple of factors. First, the one-year comparison was against a low-ebb mark. In April 2009, prices were just above a five-year low. Overall, prices are off 30% from their peak.

Secondly, the improvement came during a time when the federal government was heavily subsidizing home sales through an $8,000 homebuyer's tax credit. That credit is about to expire.

"Other housing data confirm the large impact, and likely near-future pullback, of the federal program," said David Blitzer, a spokesman for Standard and Poor's.

Once the tax credit fully expires, home prices are likely to take a beating, according to Pat Newport, a housing market analyst for IHS Global Insight.