I have a 5G 60Gig iPod I bought about a year and a half ago

There are certain albums (only complete albums) that skip on my iPod. Instead of playing the song, it cycles through the names of the songs without playing them. It slows my iPod down, which it does not respond or responds VERY slowly when I press the Menu key. I have to restart my iPod for it to work normally again.

These files played correctly on my iPod less than two weeks ago, and then suddenly could not play

I have tried everything that I can think of to solve this problem and that includes:
Reformatting the iPod – through Windows explorer and through iTunes
Restoring the iPod with the latest iPod software (through iTunes)
Manually resetting the iPod
Checking the song files to make sure they are not corrupted (They aren’t – they play fine on the computer and also play fine on my MP3 and cell phone)
Checking that the file formats and bitrates are correct for the iPod (They are)
Checking to see that the files are compressed (They are)
Making sure that the files are being converted to be compatible with the iPod (They are)
Running a diagnostic test to make sure the iPod is not corrupted (I don’t think it is)

I have looked at the Apple Support pages and they have not helped.
I googled, but no one seems to have the exactly same problem, and what solved their problems has not helped mine.

Can someone please tell me what to do with it? Thank you!