When I download Lime-Wire Basic for my mac osx it comes up blank.

Meaning usally when your done down loading a little picture will pop up that says

installer or somthing like that. But for me when it pops up it's blank i can't open it

what should I do!!?

Using Safari? Internet Explorer sometimes has troubles with .dmg files. Check that the download--usually on the desktop--ends in .dmg, and then just double-click that to get the installer. Safari has a pref that can be turned on or off to run safe downloads. Maybe see if that pref has changed.