No no no..

I need 32 bit lightmap and only ways to get them from maya2008 are tiff32 and hdr..

Please somebody test this with maya2008 create an image in photoshop then use it as an texture in maya (dont connect it to anything just load it to filenode) then try to modify this same image in photoshop and save it .. does your photoshop or any image modifieing program give you an error that the file is in use by other program or left open..