using VC6 and VAX 1418 i cannot reproduce this problem either.
on the theory that the structure name might somehow be relevant i placed the following into a .h file:
typedef struct PttAppBookObj_t
{
int nInitial;
int nSecond;
boolean pttAutoLaunchActive;
short nCounter;
} PttAppBookObj_t;
i have renamed "pttAutoLaunchActive" 3 times, and each time after giving VAX a couple of seconds to automatically reparse the file, so that the new structure component is shown as bold i hovered the mouse pointer over this new name, and the HCB jumped to this item in the structure, and showed its new name.
do you get this problem with other structures? if not can you post the complete structure you are using?