...Addons\itempreviewimprovedex\ItemPreviewImproved.lua:616: attempt to index local 'itemCurr' (a nil value)
stack trace:
...Addons\itempreviewimprovedex\ItemPreviewImproved.lua:616: in function <...Addons\itempreviewimprovedex\ItemPreviewImproved.lua:597>
(tail call): ?
ui\MarketplaceAuction\MarketplaceAuction.lua:799: in function <ui\MarketplaceAuction\MarketplaceAuction.lua:781>

Looks like this:
http://i61.tinypic.com/fnqq0x.jpg

Only the marketplace auction addon is acting up, but it's pointing to an error in both, or caused by IPIex

Should be fixed in latest version now.

I'll see if I can reproduce this over the weekend and figure out what is causing the problem.
I cannot guarantee a fix, with Drop 5 coming up and potentially other things being broken, as the source code for ItemPreviewPreviewEx is cluncky.