There is an issue in tool-tip during a debug session when a variable contains a low-value. In this case, the shown content is cut after the low-value and you are not able to see the whole content. This also happens in the auto-window and the monitor-window.
In Net Express the content was fully shown.
This behaviour is expected in Visual Studio.
The tool-tip displays the value of the item as a string and strings are terminated by a null byte. If you hover over a buffer in a C/C program containing a null byte you see exactly the same behaviour.
The tool-tip has a magnifying glass and if you click the arrow next to it and select the Text Visualizer the entire content of the item is displayed when debugging native code, with the null byte shown as '.'.