Syntax error sometimes with IO port pin assignments

Hi,

Not sure if this question should be under RX forums or here. I'm seeing errors in the e2 studio IDE regarding assignment of some IO port pins, but not all. For example:

If i write:

PORT6.PDR.BIT.B2 = 1;

this is deemed OK by the editor / builder, but if i write:

PORT6.PDR.BIT.B4 = 1;

i get a syntax error. I am only "allowed", in this case, to use something like:

PORT6.PDR.BYTE |= 0x10;

ie: address it as a whole byte, not a bit field.

Funny thing is, the processor i'm using (RX630 - R5F5630A) does have these pins. I've looked at the iodefine.h for the project and it also has B4 defined, same as B2:

...

struct st_port6 {
        union {
                  unsigned char BYTE;
                  struct {
                            unsigned char B7:1;
                            unsigned char B6:1;
                            unsigned char B5:1;
                            unsigned char B4:1;
                            unsigned char B3:1;
                            unsigned char B2:1;
                            unsigned char B1:1;
                            unsigned char B0:1;
                           } BIT;
                   } PDR;

...

It seems to happen randomly, for other ports as well or other bit fields sometimes. 

Does anyone have any idea of what might be causing this?

Thanks for any input.