ImageButton and LinkButton does not render

[MichiMichi]

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="ctl00_lnkLogin"
href="javascript:__doPostBack('ctl00$lnkLogin','') ">Logout

The proper rendered code should be:

<a id="ctl00_lnkLogin"
href="javascript:__doPostBack('ctl00$lnkLogin','') ">Logout</a>

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?