Note sure I would call it an "advanced" version of MSE. I would call it a business version. Though they use the same core, MSE is marketed (though free) for home use. Forefront for business (of any size).
In my opinion if this was coz of malware it would happen everytime but since this only happens the first time so i doubts thts the case.
I would NEVER make those assumptions.
- I would never assume malware consistently does anything.
- Most malware is poorly coded by wannabes.
- The professional malware coder strives for unpredictability.
- No single security solution is perfect.
Therefore, when it comes to malware, doubting it's malware is not good enough. ESPECIALLY when there are other networked computers with Internet access and other users who may not be as security conscious. At the very least, I would update and scan again with ForeFront and then perform a supplemental scan with a second scanner, such as the excellent Malwarebyte's AntiMalware (MBAM).
Anytime you encounter odd behavior, it is best to eliminate malware, including spyware, as the cause, or contributing factor. Hopefully, Orbital Shark's suggestion will do the trick. I wish I had remembered that one.