Avoid use of itcl scripts. It seems that for god knows what reason, tcl library I was using, was not compiled with thread support. Use of itcl, will cause heap corruptions and result to crash.
If you think, it's working 'fine' for you, you're wrong. Try running following script simultanously (repeatedly) using several clients:
bugger.itcl
set a 0
while { [incr a] < 10000 } {
;
}
*boom*
This issue applies to all versions of io, and is addressed in coming build. (it's likely, that fixed version of dll fixes problems with current build)