Too old to retrain?

Talcyon writes: I'm a 40 year old dev, and it's become apparent that my .NET skillset is woefully out of date after 5 years of doing various bits of support. I tried the "Management" thing last year but that was a failure as I'm just not a people person, and a full-on development project this year has turned into a disaster area. I'm mainly a VB.NET person with skills from the .NET 2.0 era. Is that it? Do I give up a career in technology now? Or turn around and bury myself in a support role, sorting out issues with other peoples/companies software?
I've been lurking around Slashdot for many years now, and this question occasionally comes up, but it pays to get the opinions of others...
Do I retrain and get back up to speed or am I too old?