Have you tried this particular version (wasn't totally clear from posts above)?

DynAmpWinampStartNormal true

Could there be somewhere else in your included files where that setting is being set to "false" before your desired setting is read in? First occurrence of a setting or evar has precedence with current LS builds. You could confirm the existence of the desired setting by typing this at an lsxcommand prompt:

!alert $DynAmpWinampStartNormal$

If it shows up as "true", but winamp still starts minimized, then I think you've found a bug in dynamp.