Was think fixed prior to 6.35? I am having issues with it, worse than before.
if i do this on start no problems at all:
//toolbar -as sep10 | /toolbar -az1 ffox Firefox C:\Firefox\FirefoxPortable.exe /ff
but if i do toolbar -fs then i have issues when mirc loads the toolbar or when /toolbar -fl is called, but only if i use a button picture other than default:

[toolbar]
n0=36
...
...
n34="about","About",0,"33",0,0,0,0,0,0,0,"","",0,1,0,0,""
n35="sep10","",0,"",0,0,0,0,0,0,0,"","",2,1,0,0,""
n36="ffox","Firefox",0,"C:\Firefox\FirefoxPortable.exe",0,1,0,0,0,0,0,"/ff","",0,1,0,0,""
EDIT:
can anyone confirm that this causes the same results as the image above?
//toolbar -r | /toolbar -fs | /toolbar -fl