Hi Mairi,

It's helpful to tell us what version of the software you are using?

There is an article in the KB related to this particular error for Studio 2014 (and maybe 2015...).  It's related to having an ampersand somewhere in the path, or maybe in a worksheet name, or something like this?

SDL Trados Studio and SDL MultiTerm cannot resolve the folder path or termbase name correctly because one or more folder names or the termbase name itself contain special characters. There are 2 known characters causing this behavior:

; (semi colon)

• This termbase cannot be opened because it has been created with an unsupported version of MultiTerm
• MultiTerm is unable to create the termbase. Format of the initialization string does not conform to the OLE DB specification

& (ampersand)

• Index was out of range. Must be non-negative and less than the size of the collection. Parameter name:index
• An error occurred while parsing EntityName. Line X, position XXX
• Object reference not set to an instance of an object
• There was a problem opening the termbase at C:\[folder path]\New&Termabase.sdltb. Check that this is a valid termbase and that you have permission to access it. Continue opening termbases?

Could this be your issue?

Another issue in Studio 2015 (although mainly with MIF files) is described here... worth running a verification just in case your problem is being caused by the same thing:

https://gateway.rws.com/csm?id=kb_article_view&sysparm_article=KB0037515

If none of this helps you can sometimes resolve problems like this by opening the files again as a new project, pretranslate from your TM and then save target.

Regards

Paul