I'm just noticed that oxwall trigger a warning on the member search page on a clean installation, for what I've seen apparently the issue comes from circular reference in MainSearchForm class, but it can be somewhere else :)
Disable profiler, and see if the issue persists.
To hide these errors you can do the following
in ow_core/application.php file, line 587:
before var_export, put @
do the same on line 642 and 719.