Why do I have to restart explorer.exe after bootup?

Hi, I'm new to these forums (or forums in general), so if I'm doing something wrong, please let me know...

My computer has been acting up lately, as in when I turn it on, before starting the BIOS, it sits on a black screen with a " _ " for five minutes. Then when the BIOS kicks in, it starts normally...until windows boots.

I can log in and everything just fine, but when Windows enters the "desktop" (as in, after passing the logon screen), I have a blank, black screen with just my cursor. I can still press CTRL+ALT+DEL to start the task manager and log off and such, so I go into task manager, end the explorer.exe task, and then restart it (File>New Task>explorer.exe). Then my desktop pops up, explorer starts, and everything seems fine.

Next, it takes windows another 5-10 minutes to what I want to call "configure" the network utility, as it takes that long to get a response from the notification icon or the "Network and Internet" applet in the control panel. After waiting the 5-10 mins, it starts working and connects to my network normally.

Can anyone tell me what's going on? I had a similar issue when this machine ran Vista Ultimate (x64). It didn't happen all the time, just once every month or so, and I could just restart it and it would be fine. Now that I'm running 7, restarting the PC doesn't help, and it has been happening on a daily basis for the past week. No virus scanners can find anything (McAfee, MSE, or AVG - and I only had one instaled at a time due to conflict between the programs).

Thanks Neutron16. I've talked to my grandfather who works at Intel. He thinks that all my symptoms relate to a new virus going around that actually attacks the hardware and BIOS, also affecting my antivirus (which is why none of them found anything), explorer.exe needs restarting (because it's being blocked), and my other problems.

I'll see if any heavy duty virus removal programs do the trick first, as I don't want to remove any of the customization I've done to the computer, none of which relates to the explorer.exe problem by the way.

Thanks again.

Interesting, can you post more information about the virus?