this error (SM5a1)

StepMania v5.0 alpha 1
Compiled 20120113 @ 21:38:36 EET (UTC+02:00) (build 0)
Log starting 2012-01-16 16:55:29

(stepmania:6624): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(stepmania:6624): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(stepmania:6624): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(stepmania:6624): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",
Loading window: gtk
OS: Linux ver 030000
Crash backtrace component: x86 custom backtrace
Crash lookup component: dladdr
Crash demangle component: cxa_demangle
Runtime library: glibc 2.13
Threads library: NPTL 2.13
TLS is available
Language: en
Theme: ultralight
Error: Couldn't find a sound driver that works