My Program locks out the computer from opening up any other program, drag&drop is also not working

[pma]

a user about my freeware program: "After performing any calculation, and then after closing DeskCalc SE it locks out the computer from opening up any other program, including DeskCalc SE. If I just open DeskCalc SE, and then close it without performing any calculations it causes no problems. Only when I perform calculations does it prevent me from opening any further programs, including DeskCalc SE. A reboot is the only way to solve this problem." well this has happend now a few times with win98/2000/XP, and i cant simulate it on my computers. i spend many hours to find the problem, but i'am giving up now, maybe sombody of you can help me with this strange problem.

[Rage]

Threads not being terminated ? A Hook which hooks too much ? ~RaGE();

[pma]

i use no threads in this program, but i use keyboard hooks, is it possible that key_events can couse this problems. cause one user told me that if he has this problem and is pressing "ESC" afterwards the problem is solved ?