Checking brooms for curses

[hpistheman4me]

No: HPFGUIDX 40674

Hello! My name is Cindy and I am new to HPforGrownups. I was 
wondering if anyone has any explanation for why in SS when Harry's 
broom starts acting strangely no one thinks to test it for curses. 
Hagrid even says, "Can't nothing interfere with a broomstick except 
powerful Dark magic(SS,ch.11,p.190)." Yet when Harry receives a 
broomstick from an anonymous source Professor McGonagall is quick to 
check it for every curse in the book. Of course, a escaped murderer 
is not supposed to be after Harry in SS, but obviously Professor 
Dumbledore thought there was some chance that Voldemort would come 
back for Harry or else he would not have had special things 
protecting him at the Dursley's. If this subject has already been 
discussed, forgive me. Like I said, I'm new to the community!
~Cindy~