Why doesn't kcachegrind display the call graph?

I am trying to get some information about the flow of a large program. KCachegrind used to be g开发者_C百科reat for this in the past. But the latest version (0.6kde) I have on my system (Kubuntu 10.10) won't display the call tree and caller map. It only draws a box with the current function, but no arrows and no callers. Here's the console output:

kcachegrind(27917)/kdecore (services) KMimeTypeFactory::parseMagic: Now parsing  "/usr/share/mime/magic"
QInotifyFileSystemWatcherEngine::addPaths: inotify_add_watch failed: No such file or directory
QFileSystemWatcher: failed to add paths: /home/cosmin/.config/ibus/bus
Bus::open: Can not get ibus-daemon's address. 
IBusInputContext::createInputContext: no connection to ibus-daemon 
CallGraphView::refresh 
CallGraphView::refresh: Started process 0x1346f50, 'dot -Tplain'
CallGraphView::readDotOutput: QProcess 0x1346f50
CallGraphView::dotExited: QProcess 0x1346f50

I have dot (graphviz) installed, and the application was compiled with -g -O0.

Do you have any idea where the problem could be?

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Oops... I was calling valgrind --tool=cachegrind instead of valgrind --tool=callgrind.