If you've only been printing from a single program (e.g. Microsoft Word or similar), please try printing from a different program (e.g. Notepad). If the problem persists, you'll know that the fault is definitely with your printer. If the problem disappears, you'll know that it's actually a fault with the settings within Word (or whatever).
If that test shows that it's definitely a printer fault, try uninstalling the driver, rebooting your computer and then reinstalling the driver.
If it seems to be a problem with Word (or whatever) though, start by checking that your document page size is set to A4 and that the options that appear when you click on 'Print' also show that you're using A4 paper. (Having one or the other set to 'Foolscap', or to 'US legal', can often lead to blank sheets being printed).