Does structure order matter?

Hello, I've been quite comfortable using linked list for a while now
without much hassle, but lately I've been getting problems from unexpected
places. I'm working on a graphing utility program, and to allow multiple
functions to be entered I figured the best way would be with a linked list:

struct List{
int color; /*The color it will be when drawn*/
int index; /*It's index: Y1, Y2, etc...*/
char Y[76]; /*The function itself*/
struct List *prev;
struct List *next;
}*current,*first,*hold,*last;

And I use a switch to process user input...
(Last is the last node before NULL and hold is a general placeholder)

switch(r){
case INSERT: /*When the Insert key is pressed*/
/*Do some graphics related stuff*/
/*Add a node to the end of the list*/
last->next=malloc(sizeof(struct List));
if(last->next==NULL){
puts("Cannot allocate function memory.");
exit(1);
}
hold=last;
last=last->next;
last->prev=hold;
last->next=NULL;
last->color=hold->color+1;
last->index=hold->index+1;
/*More graphics stuff*/
ggets(last->Y,76); /*<-My own string input function*/
/*More graphics stuff*/
break;

>From the above, I get errors. Running through the list is fine from first
to last but from last to first it points to garbage. But I noticed
everything seems to run fine if I put the:

last->prev=hold;
last->next=NULL;

after the ggets() statement. It's really confusing me as to why. Or is this
a different problem entirely that I may have overlooked?
I greatly appreciate any input.

Brian Dude
.

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