#1 allinanchor allintext allintitle

Nowhere to be found in first 100 normal search

[Vork]

I have a 100% white hat commercial site that never used any dirty SEO tricks - no content duplication which seems a big filter triggering factor nowadays, no keyword stuffing, no cloaking god forbid, exchanging links with websites of similar topics and not repeating the same anchor in all the links.

Upon launch (4 months ago) it was moving slowly upwards showing promosing results in sandbox and bettering with every week in normal search.
But about 2-3 weeks ago things changed drastically.
My positions for 3 top keyword sank dramatically and have been gradually sinking for the last 2 weeks.

Now as I am back at my desk after a long absence I am flooded with angry emails from a VIP customer.

This is undoubtedly a filter because allinanchor, allintitle & allinitext searches put me at #1!
In normal search however I'm nowhere in the first 100.

The only filter I can think of is notorious reciprocal linking filter.
Has anyone experienced anything alike and would like to share impressions (possible solutions)?