any word replacement bring me to login screen

hi, i’m using wordpress 2.9.2

i’ve a strange issue with any replacement plugin (text replace and also word replace) in my second wordpress site. yep coz on the first wordpress site i use text replace and it work perfectly.

the issue

when i’m in the admin panelof the text replace pugin and try to add a text to replace … when push the save button it bring me in the login screen ,, but obviously i was aready logged.

:°D the question is … simply why?

thank for any support