phranque - 8:37 am on Jul 26, 2011 (gmt 0)

clicking on any links above will not see any webpage.

googlebot's request apparently got enough of a document to extract a title element.
you should be responding to these requests with either a 301, 404 or 410 status code.

in those sub folders, no index file present, only other sub folders.

you should be responding to these requests with either a 403 or 404 status code or allow the server to create a directory index on the fly if appropriate.

i never link to them like this and certainly not using " ? "

this is ok but it doesn't solve the problem caused by google discovering these urls elsewhere.

If the problem is found from Google (HTML suggestions - Duplicate title tags report), the cause is google bot rather than other bots ?

the problem may have been discovered and reported by google but certainly wasn't caused by googlebot.

i doubt my site will be link from other sites in those linking format.

this is actually the most likely scenario but you can only be sure if you check your server access logs.
you can also find the traffic sources of your content if you have google analytics on your site.