I have the same problem, but also very expensive stuff i bought is gone. nothing helps, clearing cache i did several times but nope, lost about 20.000 sofar in phoenix, but in imprudence i have it all so it must be an SL issue.
i filed a ticket and wil wait now. im not able to buy all back because im in SL for over 4 years now and spended a lot of linden dollars.
Anyway if anyone has the the answer please let me know, i realy appreciate it.
Utopia