A contact in the UK Serious Fraud Office (who are working with the FED and other organisations in various investigations) says I can restate the following only:

1. Investigations relate to a number of things
a) Companies 'illegally' profiting
b) Credit card fraud
c) Money laundering
d) Misappropriation of funds

2. There were previous warnings issued about leaving money in on-line poker accounts
a) If the company is frozen, or is deemed to have been involved in 1 a), b), c) or d) above, you could wait a long time to get your money back if you get it at all. One of the things that has come to light is that site owners have been discovered 'withdrawing/transferring' customer monies. Hence, if they go belly up, there is not enough cash left to settle everyones accounts.
b) Whilst not an issue for the Fraud Office unless any circumstances described in 1) above are being investigated, the rules of certain sites state withdrawals can only be made via the same method as deposits. If your method of deposit has since been deemed illegal, or has been stopped for any other reason, you may also have trouble getting your money back.

Although on-line gaming is neither encouraged or condoned over here, the strong recommendation is that even if you are gambling legally, you should keep the minimum monies on deposit only.