Ok, that's what I have found.

A process may call the RegisterHotKey API function and register CTRL+C combination like any other keystroke combination. After that whenever you press CTRL+C in any application, that process receives WM_HOTKEY message. In other words, it is notified every time CTRL+C is pressed.

In FoxPro session I registered CTRL+C to main FoxPro window. After that I was not able to copy data to the clipboard pressing CTRL+C in any other application. I had to either call UnregisterHotKey or close the FoxPro window to re-activate CTRL+C.

So it might be a spyware process running on your computer. Actually when you press CTRL+C the clipboard is not changed, though a malicious process may try to analyze a foreground window.

It's really hard to guess, all I know -- you better resolve the situation asap.

Try this code:

#DEFINE MOD_ALT     1
#DEFINE MOD_CONTROL 2
#DEFINE MOD_SHIFT   4
#DEFINE VK_TAB      9
#DEFINE VK_ESCAPE   0x1b
#DEFINE VK_C        0x0043
DO decl

LOCAL hWindow, nKeyId, nModifier
hWindow = _screen.HWnd
nKeyId=1001
nModifier=MOD_CONTROL

? RegisterHotKey(hWindow, nKeyId, nModifier, VK_C)

It's likely that the RegisterHotKey returns 0 on your computer. Generally you are not able to register a hot key if this keystroke is already registered by some other thread.