The Ask.com toolbar has come under scrutiny, and is being fingered as a potential security risk. The toolbar for Internet Explorer has a flaw which affects at least version 4.0.2, one severe enough to lead to system compromise.
Proof of concept code has made its rounds around the net, so likely Ask.com is at least well aware of the flaws existence. Secunia has listed the flaw as highly critical, though disabling the toolbar altogether will prevent that from happening if you are so inclined. Ask.com hasn't commented on problem, but I'm sure there will be a fix soon.