I just heard from another board admin: A reason could have been a currently lurking "PHP-include worm" (sentry).
A rented v-server may not be the best for such a big project, so you shall better look for an own root server. This may cost a bit, but probably not the thousands of extra fee.
In Germany, there are e.g. Strato (strato.de), or 1&1 (1und1.de) - the latter seems to be approaching the international market currently.