See if any of the following help.
Try clearing Safari's cache : Settings > Safari > Clear Cookies And Data and also Clear History
If that doesn't work then try closing Safari completely and then re-open it : from the home screen (i.e. not with Safari 'open' on-screen) double-click the home button to bring up the taskbar, then press and hold any of the apps on the taskbar for a couple of seconds or so until they start shaking, then press the '-' in the top left of the Safari app to close it, and touch any part of the screen above the taskbar so as to stop the shaking and close the taskbar.
A third option is a reset : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.
Turning off iCloud and multitasking gestures on the iPad has also been suggested. Updating to iOS 5.1 could help as well.