Access vilation : pointer to a record

I have the folowing code, where lptNewMessage is a pointer to my record type (PTMessageConv).

New(lptNewMessage);
lptNewMessage^.sMessage := 'adasdasdas';
lptNewMessage^.sHasNotRead := 'asdasdasds';
Dispose(lptNewMessage);

I get an access violation error on the 3rd line. Is it because my String exceeds the allocated memory for the pointer? I don't know how the String really works, but shouldn't it take care of it's own memory needs?

Here's my record type :
PTMessageConv = ^TMessageConv;
TMessageConv = class(TObject)
sMessage : String;
sHasNotRead : String;
end;

Edit : If I swap the 2nd and 3rd line of code, it will crash on the 2nd line instead of the 3rd. And if I swap the 2 elements of my definition, it will crash on the 2nd line instead of the 3rd. So it has something to do with the last field of my record.

TMessageConv is a class not a record. If you want a record, replace with and it should work.

What you said makes sense...
But I made the change you suggested, and I have the same error.

Edit : Ok, I was using GetMem instead of New (and Dispose). It seems it's all working fine now. Thanks!