The firm might want to consider contacting the Legal Software Suppliers Association (LSSA), assuming said supplier is a member? All LSSA members are bound to a 'code of conduct' and I believe there is a formal complaints / disciplinary process.

Do you happen to have a copy of the code of conduct you can post or link to?

If you really need a Consultant to review the issues get SATURN 27 these chaps have years of experience with implementations, conversions and integrations

they could try peter owen at lights on consultany
or John Hillger
or Bill Kirby
I am sure any of these would be willing to help.

Perhaps Jim Chase Consulting can help

I'd be tempted to offer my own services but too far away for me from here up North.

A few points though.

Firstly, I want to make the observation that it is always a shame when the relationship between a supplier and client breaks down to this degree - with both parties becoming entrenched. Part of the problem here is that this was allowed to happen in the first place. IF both sides are committed to maintaining their relationship, the chances of this sort of catastrophy lessen.

Secondly, my experience of citrix is that the technology exists largely outside of the application set; apps run or don't but citrix doesn't affect them to a great degree (other than perceived speed, which is largely a bandwidth issue) once they are configured correctly. Where I have come a cropper previously is when applications interact and the citrix environment fails to deal with setting this up appropriately. Citrix itself I find to be great when it runs well; incredibly difficult to pin down when it doesn't, and I bet the supplier feels (quite confidently I'd add) that the difficulties the client is reporting are nothing to do with its app; which I'll bet runs elsewhere under citrix with no problems.

Finally; my first point of call would be with whoever is responsible for installing and maintaining the citrix environment rather than any single application supplier. LEt them act as honest broker.

I would tend to agree this is a Citrix issue, not the native application. If it works outside a Citrix environment then that should absolve the PMS supplier (apart from their apparent attitude issue - after all, if it is someone else's fault they should be able to make money from the situation)

Is this a "plug your own consultancy in an anonymous fashion" thread ?
As someone on the law firm side, 4 more for the pot - Phoenix, Kestrel, NCCG, VProfessional

Not trying to plug any of consultants, but some are ok.
As Andy says in general Citrix once set up right generally works well, and certainly the recent versions have been a lot less trouble than earlier ones.
I suspect from the note from the practice that there is some confusion over what is not working. Most suppliers do not have a Citrix version. Their system simply works with in the Citrix . Sounds to me as if the citrix supplier, the pms supplier and the client need to sit down and work out who needs to do what.
Good luck to them though if their citrix supplier does not know what they are doing it could take a while to sort.

Many thanks for all your responses - I think the firm is now talking to a couple of consultants

If all else fails you could always try Giles Coates.