Quote marks in WPA PSKs aren't properly handled by ifup-wireless -- the 'SUFFIX' probing around line 515 chokes on the quotes (other uses of eval+echo are similarly brittle).  Command-line reproduction:
 
   $ SUFFIX=''
   $ WIRELESS_WPA_PSK="\"Why, Linux,\" I'd replied."
   $ L="`eval \$WIRELESS_WPA_PSK$SUFFIX`"
   bash: eval: line 1: unexpected EOF while looking for matching `''
   bash: eval: line 2: syntax error: unexpected end of file

A less legible command substitution/eval+printf can handle this, however:

   $ SUFFIX=''
   $ WIRELESS_WPA_PSK="\"Why, Linux,\" I'd replied."
   $ L=$(eval printf '%s' \"\$WIRELESS_WPA_PSK$SUFFIX\")
   $ echo $L
   "Why, Linux," I'd replied.

(Now, whether or not YaST can convey the quotes properly and whether wpa_supplicant files are correctly written is a different matter...)

Thanks,
Mike