<hr /><i>rkeene added on 2010-10-16 21:12:41:</i><br />
The issue only occurs when using [fcopy] and mk4vfs channels without direct mode.

Simple test:
<verbatim>
vfs::mk4::Mount test.mk /TEST
set fd [open /TEST/cross.png]
fconfigure $fd -translation binary
set out [open /dev/null w]
set ::fcopy_complete 0
proc fcopy_complete {args} { set ::fcopy_complete 1 }
fcopy $fd $out -command fcopy_complete
after 3000
update
puts "FCOPY: $fcopy_complete"
</verbatim>