Ok, only had this problem in a Haier 22" TV (except it was a pure VGA connection, no converting). I wound up using an old Altinex 2x1:2 2x1 VGA switcher. This switcher had an RGBHV output via BNC connectors with a buffered output. When I used this, the image as in the centre.
A great deal of TV's are not supporting VGA unfortunately, although I know you are using a HDMI connection to your tele via the converter. Most TV's do not have much support for the HDMI being the HDCP/EDID communications that occur also dictate the resolution and other aspects of the signal - once again depending on you tele's chipset and how it interprets communication from a VGA to HDMI converter.
The converter may be the problem as it is most likely not a scaler. IF it is, please give use some more details like the model number of the make/model tele and converter.