I think I've a little workaround for this issue. Perhaps it helps someone of you. However, you've to download and install an extra program (named AutoHotkey).
The idea is to write a script, which activates the "playlist search" window after it has popped up. AutoHotkey provides an own scripting language with which you are able to map a lot of great functions to almost any key combination you wish. In this case I used it to activate the "playlist search" window right after it has popped up.
Here's what you have to do:
1.) Set a global hotkey in foobar for calling the "playlist search" window (in my case it's ctrl-j)
2.) Download and install latest version of AutoHotkey from
http://www.autohotkey.com/download/3.) Create a new text file with notepad or any other editor and insert the following script code:
QUOTE
;AutoHotkey workaround for "playlist search" focus bug in foobar2000
$^j::
Send, ^j
WinActivate, Playlist search
return
4.) The above script code is only suitable if you use ctrl-j as global hotkey for playlist search (like I do). If you've set another hotkey in foobar, you've to replace the two "^j" by your hotkey combination. ^ is the symbol for the CTRL key in the scripting language of AutoHotkey. # is the placeholder for the windows key, ! stands for ALT and + for SHIFT. You can just combine them to create the key combination you need. For example if you've set in foobar the key combination SHIFT-ALT-7 you would have to replace the two "^j" by "+!7"
5.) Save the file as foobarworkaround.ahk or something else. The name isn't important but the ending has to be ".ahk"!
6.) Start this file by double clicking it. I don't know if a restart of windows after the setup of AutoHotkey is needed for this step to work properly, so just try. If you can see a little green icon with an "H" on it in your system tray the script has loaded succesfully. Now test the script by pressing your global hotkey for playlist search. The playlist search window should pop up and you should be able to type in a search immediately.
The above script works for me. If you encounter problems with this workaround let me hear and I'll try to help you.
Hope this helps a bit till the bug is fixed.
[edit]: added $ in script right before the hotkey setting. Prevents the script for starting an infinite loop, if Playlist search window doesn't open. Seems to happen sometimes. Maybe another bug in global hotkeys setting of foobar?