As long as the motherboard natively supports the memory at the rated speed, it is perfectly safe to use any memory module irrespective of the CPU's FSB speed.. So check with your motherboard specifications.. If it memtions DDR2 667 as supported then you have nothing to worry about..
For your cpu 533 is actually 1:1 not 1066. cpu = 1066QDR(Quad) mem = 533DDR(dual) its all a base clock of 266
There was not even such a thing as 1066mhz ddr2 when they released the 945 chipsets.
That said, i have used DDR2 800 (6400) on boards that ran at 533 without issues as well. the DDR 533(5300) should work without issues.
Please note some memory does not run on the default voltage and requires a bit more voltage, but this is generally limited to DDR 2 @ 800(and only when running at those speeds with tight timings) and higher so you should not have to deal with this.
Final word, it will work just fine, you can even run it at 667 if you want. There will be an option in the bios for you to change it.