Quoted from:
http://www.cypheros.de/tsdoctor_faq_e.html#3.2
****> 3.2 This error occurs when the TS-Doctor has found a manipulation of the system time. A reset of the date to the correct date is not fixing this message. You need to remove the TS-Doctor completely and then reinstall it. To completely remove, uninstall the TS-Doctor and by using regedit, delete the key "TSDoctor" which can be found here : HKEY_CURRENT_USER\Software\Cypheros\ <<<
(You need admin rights to delete the key)
Then You should download latest version and reinstall TS-Doctor.
In case you don´t install TS-Doctor under your admin account, the program must be installed with admin rights (WinXP: RunAs) under the (non-admin-) user account , where you want to use the program. (Vista and Win7 will automatically ask for admin permission).
After installation TS-Doctor doesn´t need any more admin rights to run.
Best is to install it under admin account and use it there.