the installer works fine till the page where we have to select between the partitioning type, there i select the 3rd option (manual partitioning), then its starts analysing partitions, till 60% it goes ok then the analyzing stops and i'm directed to next page (where i should see all the partitions listed and options to edit them) but that page is blank

, only the message at the end shows up which says "remember to allocate minimum 2 gb for / partition etc etc..", but the continue button is still there, i click on it nothing happens, i click on it again and it says "installer carshed" and mentions the bug in detail. i'm confused
then i tried to open qparted and the same happened with it, it analysed the partitions till 60% and poof it crashed
ps i have tried safe mode and another disk too, so its not a problem in the media.
i think the problem is with the ext3 partition which already exists (the one in which ubuntu is installed) cause konquerer only shows up my ntfs partitions, no sign of ext3 partition in konquerer.