6510 bug?

5 days ago I have buy a 6510 and saturday it has happened that when I make one telephone call, it appears up on the left the symbol of the "sure logon wap (open.. The little padlock open)... it is appeared also Sunday when I was writing a sms...
When it appears the telephone is not resetting itself but it continues to work perfectly! ...the small padlock is appeared for least (about 0.5 sec and after it is disappeared).
This morning I have restored the factory default setting &, from now, the padlock does not appear more.

What's appened??? Is a bug?

PS: except the padlock, I have not never seen telephone resetting itself!

ah... can someone explain the bug into nokia 6510 sw 4.00?

& the improvement after 4.00 version.. please ?

Thank U & sorry 4 mY bad English :(