I had this same shit done to me just 2 days ago, and just like you
i called them up and asked for a reason but all they told me was
the same thing stated in the email i got from them
Unusual account activity has made it necessary to limit account access until additional verification information can be collected.
i didn't give up and asked for a reason over and over but they only told me that they
"found my account was too risky and they think that its better to terminate my account"
so i asked why risky? and they answered , "we don't know" , "we cant tell you"
"its not that you've done something wrong , it could be that you were linked to
a fraud account" and a whole lot of other BS.
so i spend the next day with my friend (who is a lawyer) and we went through the
paypal user agreement , and there is really nothing we could do.
the only thing i can do now is start a new one and hold for 6 months
for them to release $7852 of my hard earned money!