acrobat freezing across several computers

I'm in an office with about 11 computers - some of these are running Windows Vista, some of them are running Windows XP (I think all SP3). They are all Dell computers, with one custom-built exception. On most of the computers running Windows XP, Acrobat Pro 8 and 9 will periodically freeze when a pdf is opened. Updating Acrobat, deleting acr*.tmp files, and recreating Acrobat preferences have had no effect on the problem. The systems are clean in terms of viruses and spyware.

The prior IT tech has hinted that the fact that the PDFs are usually taken from a virtual server may be to blame - but I can't imagine this is the case.

Services running include Acronis True Home Backup, ESET NOD32, Affixa, and JungleDisk.

The jerks at Adobe hang up every time I call. Please help!