there is a bug with scon, when you have two or more connection (multi-server). where one of connection id are greater than 11.

Code:
how to re-produce:
1. run your mIRC ;)
2. //var %x 1 | while (%x <= 15) { sockopen %x localhost 80 | sockclose %x | inc %x }
   note: it will make it faster to reach connection id greater than 11
3. open new server window (do not connect it), ie: /server -n irc.dal.net
4.  back to first connection id (ALT + 1)
5. //scon $scon(1) echo -s ::: scon test $scon(1)
6. //scon $scon(2) echo -s ::: scon test $scon(2)
   as result, you may get following error: * No such connection id: 16
7. but the correct connection id should be 18, //echo -a ::: $scon(2)

Charlie