First suspension doesn't work, need to perform twice instead

[rvitulli]

Hi,

Whenever I perform a system suspension I have to act it twice to let it work:
after the first try the screen turns black seeming to go on suspension
but after a while it shows a locked screen asking for password;
once unlocked the screen, after a second request the system finally goes into suspension.

Any further suspension request works perfectly.

Any idea?

Consider that I've noticed this issue on different Ubuntu versions

Thanks in advance

My system:
Asus EeePc 1000
Ubuntu 10.04 Netbook Edition (x86)