Hi. Where are you searching exactly?
In the Search bar at the top of the Media Library > Local Media > Audio view?
Or in the Jump to File window via Playlist > J ?
If in Local Media > Audio, please confirm that you've installed the Winamp 5.3a Update Pack which includes an update ml_local.dll
Alas, we can't reproduce the problem.
Could you also provide some examples of what you're typing into the Search field?