I've been having some problems with "or" in queries.

If I do a query for "science or technology" in my index, I get (say) 32
hits, but if I do a search for "technology or science", I then get another
number (say) 53 hits. This should never happen, right? 

Also, if I have a complex query using metatags like 
	science or technology and metaone=this and metatwo=this or that

this also doesn't work (no results, when I definitely should have some),
but if I do either:
	science or technology and metaone=this and metatwo=this 
or
	science or technology and metaone=this and metatwo=that

I do get results. 

I think this is a genuine bug... any idea what's going on? 

Thanks,
RL