If you want to burn CDs with iTunes, you can't use Toast. You must disable the "Toast USB Support" extension and the "Toast CD Reader" extension. You will not be able to use any of the functions of Toast.
If you want to use Toast to burn, you must disable the "Authoring Support", "USB Authoring Support" and "Firewire Authoring Support" extensions installed by iTunes. You can still use all other functions of iTunes, including encoding CD tracks as MP3 ("Import").
You cannot switch between using Toast and iTunes for CD burning without disabling and enabling the appropriate extensions and restarting. If you really want to do this, then you should create two extension sets and switch between them (you'll still need to restart).
As iTunes can ONLY burn audio CDs, I don't use it for burning, as Toast 5 can do this and everything else (except sadly, CD-Text). If you want to use Toast to burn Audio CDs from your MP3s, all you have to do is drag your playlist from iTunes onto the Toast window. Toast 5 can burn in the background. It's well worth the upgrade from Toast 4.
Still, hopefully, Apple or Roxio will fix the incompatibility soon and we'll be able to use both.
------------------
#define m(i)(x[i]^s[i+84])<<
unsigned char x[5],y,s[2048];main(n){for(read(0,x,5);read(0,s,n=2048);write(1, s
,n))if(s[y=s[13]%8+20]/16%4==1){int i=m(1)17^256+m(0)8,k=m(2)0,j=m(4)17^m(3)9^k
*2-k%8^8,a=0,c=26;for(s[y]-=16;--c;j*=2)a=a*2^i&1,i=i/2^j&1<<24;for(j=127;++j<n
;c=c>y)c+=y=i^i/8^i>>4^i>>12,i=i&g t;>8^y<<17,a^=a>&g t;14,y=a^a*8^a<<6,a=a>> ;8^y<<9,k=s
[j],k="7Wo~'G_\216"[k&7]+2^"cr3sfw6v;*k+>/n."[k>>4]*2^k*257/8,s[j]=k^(k&k*2&34)
*6^c+~y;}}