my 99 a3 GLX has the same problems.... 2 nights in a warm garage (60 F), park outside in cold... will get frozen locks... never the back doors though?? i think that some faults in the alarm/power lock system are tripping for you... this will create unpredictable results, as i too have observed. jeremy 99 glx/arctic silver/blaupunkt-bose (yes, it works!)