I have not seen this problem on my iPad 2 with iOS 5 but I offer this workaround, at least until a fix is released or found.
Instead of just clicking a link then using the back button to return to the original page, open the link in a new tab. Then when you are finished reading the article close the tab. I often go through a forum or list of articles and open several tabs at the same time. Then, when I'm finished with an article or post, I close that tab. Eventually, if I have a bunch of tabs open, I'll get back to the original page.
On an iPad 2 running iOS 5 you open a link in a new tab by using a tap and hold gesture. After a short hold on the link you'll get a list of options:
Open - opens the link in the same tab, i.e. replaces the content of the tab with the contents at the link.
Open in a new tab - opens the link in a new tab.
Add to reading list - adds the link to the reading list section of the History icon.
Copy - copies the link so you can paste it in a message ,email or browser address section.