ImageButton and LinkButton does not render

Having a strange problem with the ImageButton and LinkButton on a
masterpage which does not completely render the proper HTML code.
Instead the "<" sign gets somehow messed up and as a final result the
entire string is shown on the page.

Example: p?`d=3D"ctl00_lnkLogin"
href=3D"javascript:__doPostBack('ctl00$lnkLogin','')">Logout

The proper rendered code should be:

href=3D"javascript:__doPostBack('ctl00$lnkLogin','')">Logout

This error happens not all the time. I would say about 50%. When I
reload the page, sometimes the proper HTML code is rendered. It almost
like playing roulette :) On some pages is works 100% on others not.

Any ideas from a Guru?