I have a strange problem in QGIS 2.2 (problem is also present in QGIS 2.1). When I add a point (shapefile) layer, apply graduated style and change point size, everything looks fine. Then I save project, reopen it, and some of the points are missing.
When I open attribute table all points are there, but some of them are not shown on the map. Usually those point are in the middle of the map. I noticed that number of mising points depends on selected "on the fly" CRS (before save). When I remove graduated style then all points show up on the map... Zooming, refreshing view and changing projection doesn't help.