Joomla Expert Bugfixing Needed

Website type: holiday homerental, CMS: Joomla 1.5, Joom!fish Multilanguage, [login to view URL] Problem: The website main tab links keeps changing spontaneously. The strange thing is all other website links are always correct. During development of the website, the website was installed on a temp link [login to view URL]~p27386/ because the domain name [login to view URL] was not active yet. Somehow the website keeps changing the main tab links into the old website link [login to view URL]~p27386/. When using the HOME tab once all main tabs keep working using the above url. However when typing [login to view URL] again in the browsers address area again all main tabs are not working any more except the HOME tab which refers to [login to view URL]~p27386/ Another strange thing is that sometimes the main tabs do have the right links. The website is multilangual in three languages. The above occur in all the three languages. It seems the base url is sometimes not correct as also some recurring process is changing the main tab links into [login to view URL]~p27386/ and visa versa. The strange thing is that above problem happens random for all languages or sometimes only for one language. Again it only effects the top menu (main tabs)! Clearing cache does not do the job.