Sharepoint 2010 FBA users not found in People Picker

In IIS Manager, browse to the Central Admin web application. Explore the folder and find the web.config file. Open in Notepad.
Find the <PeoplePickerWildcards> node and use the following:

<PeoplePickerWildcards>

    <clear />

    <add key="FBA" value="%" />

  </PeoplePickerWildcards>

still if you are having same problem follow this post, it could be sql server permissions issue.

http://suryapulipati.blogspot.com/2012/06/exception-occurred-when-trying-to-issue.html