I had the same issue back in January and complained immediately to PayPal, primarily because I have an immaculate record going back over five years and they told me that, to quote, "there may be a higher than acceptable level of risk or exposure associated with your Account (based on the information available to PayPal at the relevant time and what in its sole discretion it regards as an acceptable level of risk or exposure to PayPal under all the circumstances)".
They initially told me that this was to become a permanent policy and that if I didn't like it I was at liberty to close my account. I told them that there was no point in my doing that as I still wanted to be able to pay using PayPal, and that I would just stop offering it as a mean of payment in my auctions. After hearing nothing back for a few weeks, I eventually received an email saying that because of my "consistently good performance" (even though I had not actually used PayPal in those few weeks) the restrictions on my account were being lifted.