A complaint of "burning" with no obvious source would seem to indicate neuropathic pain.
Although rare on its own, trigeminal neuralgia (or some variant) is statistically more common in women over age 50.
This case also made me think of something like postherpetic neuralgia. I guess the lack of sores or lesions would make identification more confusing.
The association between HSV-1 and a migraine-like headache is interesting too.
Although not well demonstrated, another intriguing association with HSV is the potential increased risk of Alzheimers in certain genetically susceptible individuals: http://en.wikipedia.org/wiki/Herpes_simplex_virus#Alzheimer.27s_disease
For the elderly in the U.S., it looks like prevalence of HSV-1 in non-high-risk groups is estimated to be around 80-90%.
If anyone is interested in looking through some data, Tables 1 & 2 list HSV prevalence by continent, country, and study year through 2002:Age-Specific Prevalence of Infection with Herpes Simplex Virus Types 2 and 1: A Global Review: http://jid.oxfordjournals.org/content/186/Supplement_1/S3.long