I don't know how exactly how managed to create the drafts this way,
but I have several emails in my Drafts folder with
    X-Evolution-Account: 1120811084.728.0@debian
in the header. They might have been created with Evolution 2.4
on Ubuntu Hoary and then copied over via rsync to my current machine,
running a self-compiled Evolution 2.4.2 with Garnome 2.12.2.

When opening one of the email with the invalid/unknown account
infos, Evolution segfaults in e-msg-composer.c, line 4217:
         if (account_name) {
                 account_name = g_strdup (account_name);
                 g_strstrip (account_name);
                 
                 if ((account = mail_config_get_account_by_uid(account_name)) == NULL)
                         /* 'old' setting */
                         account = mail_config_get_account_by_name(account_name);
                 g_free (account_name);
4217 =>          account_name = g_strdup (account->name);
         }

The reason is that account is NULL. I checked it manually in a debugger,
neither of the two calls to set it return a value. I assume that
the account UID is no longer valid. As I said earlier, I don't know exactly
how I managed this, but I suppose one can reproduce it in several ways:
- delete an email account and create another one
- copy a draft folder from one machine to another
- migrate from one Evolution to another

The solution to the problem is simple, just change
   account_name = g_strdup (account->name);
into
   account_name = account ? g_strdup (account->name) : NULL;

I checked the latest revision (1.526), the problem still exists there.

I verified that the suggested change causes no problems in a debugger: 
account_name is only used in a call to e_msg_composer_set_headers() and
that seems to work just fine with a NULL parameter.

For the record (and please don't ask me for a gdb backtrace of all threads,
I don't think it is necessary and I don't have Evolution running inside gdb),
here's the stack backtrace:
C    e_msg_composer_new_with_message, FP=bfffcb88
C    edit_message,         FP=bfffcba8
C    edit_messages,        FP=bfffcbd8
C    get_messages_got,     FP=bfffcbf8
C    mail_msgport_replied, FP=bfffcc28
C    g_io_unix_dispatch,   FP=bfffcc58
C    g_main_dispatch,      FP=bfffcca8
C    g_main_context_dispatch, FP=bfffccd8
C    g_main_context_iterate, FP=bfffcd48
C    g_main_loop_run,      FP=bfffcd88
C    bonobo_main,          FP=bfffcda8
C    main,                 FP=bfffcee8
     __libc_start_main,    FP=bfffcf08