Problem with pager

Hello everyone.

I have a drupal site that stores a lot of products, so I need a search 
engine.

In the search engine there are four  radio buttons to selecting search 
options.

Initially the search engine works perfectly, but when I do a search 
without labeling any of the four  radio buttons and the search results 
are paginated comes trouble.

The first page is displayed without problems, but when I try to access 
any of the following pages automatically the four radio buttons are 
labeled and highlighted in red, throwing an error saying:

- Detected an illegal option. Please contact the site administrator.

I do not know what could be the problem, until recently has been working 
perfectly, but after a few updates in the the core and modules, the page 
throw this error.

Any ideas?
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