Setting onmouseover attributes of label in code behind

 In my code behind I set the mouseover attributes of a label using variable created from the database like this for example:
Label1.Attributes.Add("onmouseover", "return overlib('Language: " + sLanguage + "');");
When I then click a button on the page that causes postback and whilst the page is posting back I mouse over the label I have declared above, the page stops posting back and as such the button event does not occur.
Any ideas why this is happening or a way around this?
Thanks for looking.
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