Help: Problems logging into Primavera

Hi everyone

I'd be really grateful for some help please!  I desperately need to get cracking on some important work today and can't get back into P5.  I get the following error message.

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I had this problem ages ago and seem to recall that I just needed to clear a log file somewhere or something simple like that, but can't quite recall at this stage.  Any help to get this resolved gratefully received.

Thanks in advance

Andy